[ds_tx]

I saw that and checked the end tags. There's nothing wrong with them. They're preceded by / and enclosed in less than and greater than symbols as they should be.

[black_eagle]

Just post a copy of the file somewhere.  There is a reason that Kodi is complaining about it.  Make sure it is the actual file that Kodi is trying to read and not the one from your Mac.

[ds_tx]

Now debugging log is saying 
ERROR: Create - Error( Invalid argument )
ERROR: Create - Error creating /storage/.kodi/userdata/playlists/music
ERROR: Create - Error creating special://profile/playlists/music

No Mac version for Notepad++, so someone saved file on Notepad++ for me in UNIX format, because they thought that might be an issue.
Then added end tags to comments because they were causing color flags to xml code.
That's when the above errors appeared.
After deleting comments completely, above errors persist.

See -
http://dstall.com/advancedsettings.xml
http://dstall.com/01_KODI.log

Forum only allows me 8 comments per day, so I'm going to get cut off here soon.

[black_eagle]

Your log there shows the advancedsettings.xml file being correctly loaded.  And it shows Kodi setting up the path subs correctly.
Then though, it shows an error when trying to (I presume) write to those directories.  Your playlist directory at the very least needs to be writeable by Kodi as it expects to be able to save playlists in it. I think
 

2019-04-11 16:28:38.214 T:4060606480 DEBUG: Configuring path substitutions
2019-04-11 16:28:38.214 T:4060606480 DEBUG: Registering substitution pair:
2019-04-11 16:28:38.214 T:4060606480 DEBUG: From: [/storage/.kodi/userdata/playlists/music/]
2019-04-11 16:28:38.214 T:4060606480 DEBUG: To: [smb://1.MacDOCS/Music/]
2019-04-11 16:28:38.214 T:4060606480 DEBUG: Registering substitution pair:
2019-04-11 16:28:38.214 T:4060606480 DEBUG: From: [\\1.MacDOCS\Music\]
2019-04-11 16:28:38.214 T:4060606480 DEBUG: To: [smb://1.MacDOCS/Music/]
2019-04-11 16:28:38.215 T:4060606480 NOTICE: CMediaSourceSettings: loading media sources from special://masterprofile/sources.xml
2019-04-11 16:28:38.224 T:4060606480 ERROR: Create - Error( Invalid argument )
2019-04-11 16:28:38.225 T:4060606480 ERROR: Create - Error creating /storage/.kodi/userdata/playlists/music
2019-04-11 16:28:38.225 T:4060606480 ERROR: Create - Error creating special://profile/playlists/music

[ds_tx]

So how do I make playlists writeable?
Do I add code to Kodi library/music/playlists.xml file?
If so what?
I dont' see anything in there now but icon for DefaultMusicPlaylists.png and path - special://musicplaylists/
Playlist .m3u files exported from iTunes do not have any permissions associated with them that I can see with Get Info command on Mac where permissions are normally set or changed.
I've copied playlist m3u files to Kodi userdata/playlists/music on N2 CoreELEC as well as Mac, and they work fine with Kodi on Mac

[black_eagle]

Does the smb user have write access to the directories you are re-mapping with path subs ?

When you set up an smb share, you generally set it up for a specific user (with a username and password to connect with) or as a guest account which does not need authentication. I have no idea how it works on a Mac but on Ubuntu, I have an smb.conf file in /etc/samba that specifies the shared directories and whether or not they are writeable, browseable and able to be accessed by a guest account or not.

EG

php:
[KidsTV]

    path = /media/sde1/KidsTV

    writeable = yes

    browseable = yes

    guest ok = yes

[ds_tx]

Issue is not with Mac Kodi app.
Issue is with Kodi on CoreELEC.
Where is smb.conf file stored in Kodi on CoreELEC?
Do I need to modify smb.conf file for Kodi on CoreELEC for my 1.MacDOCS external HDD?
In file, enter [1.MacDOCS]/ instead of [KidsTV] ?
Would path to my external HDD be -    path= /media/sde1/1.MacDOCS  ?
To what does sde1 refer?

[black_eagle]

Issue is not with Mac Kodi app.

No, I know.  I think the issue is with your smb settings on your mac.

Where is smb.conf file stored in Kodi on CoreELEC?

It isn't.  Its on the machine that is sharing the files.

In file, enter [1.MacDOCS]/ instead of [KidsTV] ?
Would path to my external HDD be -    path= /media/sde1/1.MacDOCS  ?
To what does sde1 refer?

1) Most likely yes, although if you have set it up properly, that should already be present in the file
2) No, your path should refer to wherever your Mac mounts the external drive - in the example from one of my shares, the drive sde1 is mounted in /media
3) sde1 refers to a drive in a server on my network and was only meant to be an example of how a correctly shared directory appears in the smb.conf file.

[ds_tx]

No, the hardware is Odroid N2 CoreELEC, not Apple MAC.
CoreELEC is the OS, and Kodi is embedded (I suppose you could say) in/with the CoreELEC OS.
Mac has nothing to do with it.
1.MacDOCS is external HDD connected to Odroid N2 CoreELEC.
Everything works fine on my MAC install of Kodi - that's why I said issue is not with Kodi on Mac.
Issue is with Kodi running on CoreELEC with Odroid N2 hardware (an SBC - single board computer).

In Configfiles folder on CoreELEC, there is a samba.conf.sample, but no smb.conf file.
Samba was originally smb server but name was changed (See Google)
In Configfiles > system.d - there is also a nfs.mount.sample

See http://dstall.com/samba.conf.sample.txt

[black_eagle]

No, the hardware is Odroid N2 CoreELEC, not Apple MAC.
CoreELEC is the OS, and Kodi is embedded (I suppose you could say) in/with the CoreELEC OS.
Mac has nothing to do with it.
1.MacDOCS is external HDD connected to Odroid N2 CoreELEC.
Everything works fine on my MAC install of Kodi - that's why I said issue is not with Kodi on Mac.
Issue is with Kodi running on CoreELEC with Odroid N2 hardware (an SBC - single board computer).

In Configfiles folder on CoreELEC, there is a samba.conf.sample, but no smb.conf file.
Samba was originally smb server but name was changed (See Google)
In Configfiles > system.d - there is also a nfs.mount.sample

Yeah, I know what your hardware is.

I have to ask though,  your very first post about this shows you trying to path substitute an SMB share

<pathsubstitution>
        <substitute>
            <from>special://profile/playlists/music/</from> <---This line is the Kodi default playlist path/directory, "special" replaces a long user related path)
            <to>smb://MacDOCS/Music/</to> <----This line "maps" the line above to my NAS path for my m3u files from media monkey
        </substitute>
        <substitute>
            <from>\\MacDOCS\Music\</from> <----this line is the path to each song contained within the m3u files, relative vs.absolute path
            <to>smb://MacDOCS/Music/</to> <---this line maps the line above to the Kodi friendly path of my NAS song directories
        </substitute>
    </pathsubstitution>

Is it just an external drive or is it a NAS drive ?  The two things are completely different.

[ds_tx]

It's strictly an external drive attached to the N2, just as I strictly have an externaldrive attached to my Mac.
No file sharing involved.
The path substitution you posted is the one I use for my Mac system with Kodi app.
It works just fine on Mac.
I used same path substitution for N2 but renamed hard drive to the drive I use with N2 (1.MacDOCS) which is a backup clone of the drive I use with my Mac (MacDOCS)
So everything's the same for N2 as on Mac except name of hard drive.
I did the same thing with the playlist .m3u files - changed all code from MacDOCS to 1.MacDOCS
so playlists point to the 1.MacDOCS external drive that's connected to the N2,
just as playlists for Kodi on Mac point to the MacDOCS which is the external drive connected to my Mac, where playlists play just fine.

[black_eagle]

Right well if it's just an external drive then SMB is not involved at all and is completely irrelevant (hence why I'm not sure you have it in there, or indeed how it can possibly work on your Mac).

Anyway, what you need to do is find out where the Odroid mounts the external drive and make the path subs point to it.

Although I have to say, it would be much easier just to plug it in and add it as a source in Kodi.

[ds_tx]

I've already added the music folders on the external drive as media sources in Kodi and can play music from the Music Homes Screen.
But I want to play music from playlists in Kodi/userdata/music/playlists/jazz.m3u (for example)
However, playlists point to external drive.
So how do I make playlists point to Kodi.
Please explain alternatives to the following playlist -
#EXTM3U
#EXTINF:300,Dream A Little Dream Of Me - Ella Fitzgerald
/Volumes/1.MacDOCS/Music/_iTunes/iTunes Media/Music/Ella Fitzgerald/All That Jazz/01 Dream A Little Dream Of Me.m4a
With what do I replace the first part of the path that points to the external drive? -  
/Volumes/1.MacDOCS/Music/_iTunes/iTunes Media/ ?
Music folder in last part of path is the media source folder that's been added to Kodi - 
/Music/Ella Fitzgerald/All That Jazz/01 Dream A Little Dream Of Me.m4a

[ds_tx]

Path substitution is point to the external volume, remember?
<pathsubstitution>
        <substitute>
            <from>special://profile/playlists/music/</from> <---This line is the Kodi default playlist path/directory, "special" replaces a long user related path)
            <to>smb://1.MacDOCS/Music/</to> <----This line "maps" the line above to my NAS path for my m3u files from media monkey
        </substitute>
        <substitute>
            <from>\\1.MacDOCS\Music\</from> <----this line is the path to each song contained within the m3u files, relative vs.absolute path
            <to>smb://1.MacDOCS/Music/</to> <---this line maps the line above to the Kodi friendly path of my NAS song directories
        </substitute>
    </pathsubstitution>
That works just fine on Mac with external drive MacDOCS, but not on CoreELEC with external drive 1.MacDOCS

[black_eagle]

Sigh.  You don't have a NAS. You have an external USB drive.  There is absolutely NO network protocol involved with an external drive like that so smb:// will never work as what you are telling Kodi there is to fetch the files from an SMB server somewhere on your network called 1.MacDOCS that is sharing a directory called Music.   But, as you've now stated this is just an external drive then there is no smb server to fetch the files from.

Those path subs you have posted point to an smb server, not an external drive.  The two things are completely different.

Here's a suggestion for you.  As you have added the drive as a source and can already play music from it, drop your path subs for the moment from your advancedsettings file.  Make one playlist with Kodi that uses some music from the drive. Save it.  Verify it plays. Open it in some text editor and see what the paths are.  Either create some path subs to remap directories based on those paths you see, or edit your playlists to reflect the correct paths.

Although, everything you have said in this thread (which is meant to be a feature request, not a help thread on how to do something) is totally confusing.

It's strictly an external drive attached to the N2, just as I strictly have an externaldrive attached to my Mac.
No file sharing involved.

Yet you also say

  <to>smb://1.MacDOCS/Music/</to> <----This line "maps" the line above to my NAS path for my m3u files from media monkey

 What NAS ? And why have you got a file sharing protocol in there when you have said "No file sharing involved" ?

So, as I can't make head or tail of what actual equipment you have and how exactly it's connected because you seem to change your mind every three posts, then I'm afraid I can no longer offer you any help. Good luck with getting it sorted though.