[DaveBlake]

Thanks for nice explanation @Karellen, but disappointed you found operation a little confusing @scott967. Actually I don't understand how hiding unused fields, and adding some text that explains what an option does can make it more confusing, so surely this is better and you were even more confused before? Lets try to dig into this - not to prove my rightness, but to try and see if things can be improved further.
 

In the past export to separate files required the designation of the  "destination folder" on this same settings dialog. 

And it still does, this has not changed.
 

...I guess changed behavior of "to library folders"  send the export to the "artist info folder" which is set elsewhere, and not to the "destination folder" that used to be set here. 

Again I think you misremember, "To Library folders" has never allowed entry of destination folder here. Its function is to export artist stuff to artist folders in the Artist Information Folder and album stuff to the folder containing the music files for that album (providing it is unique to that album). This has not changed.

 

It seems like it should be possible to use the "destination folder" for these options as well,

Yes it is. Using "To separate files" you can export NFO, art or nothing (for artists only) that makes empty folders, to a destination of your choice.

 

...also needs to be made clear to user (maybe in wiki if not in the settings help textbox) that the "artist information folder" must be set elsewhere. 

Yes the functionally rich export facility needs a clear wiki. I strongly believe in giving expert users the power to do things in Kodi, but the trick is doing that without confusing the novice. Export is on the border of this, and I'm sure some people would remove it because of that. I hope we can work to make it as intuitive as possible instead.
 

Also now I see we have a button on the dialog window where the onclick is a noop.  I assume that doesn't cause any problem.

No problems as far as I know.

 

So I guess we can say that we will never export nor scan the "source" folder tree for artist nfo or art?

The intention is to encourage users to use the Artist Information Folder because it offers so many advantages, but not to compel. This means that scanning is backwards compatible and will look for album artist nfo and art in a folder above the album folders providing a folder unique to the album artist can be found.

Exporting to a source folder can get very messy, hence discouraging it. To do the reverse of the backwards compatible scanning could be so confusing e.g. only album artists with unique folders (containing all music by them and only them) could have nfo and art exported. What to do with the rest?

However if the user wants they can limit themselves to one music source, set the AIF to be that source and have music in artist folders immediately beneath it named precisely, and containing music by that artist and only that artist. Then export "to library folders" will in effect put the output in the source tree. Likewise they can use "To separate folders" to achieve the same.

What export in v18 (not new to recent PR) won't do is put artist stuff in the folder above albums regardless of folder name. It will scan from there, but not export to it. It means that while users can fetch album artist stuff from the original places, they can't easily put it back there using export, but they can easily put it somewhere better.
 

Or if the user does nothing in settings, we still can get artist art/nfo from the "source", we just can't export artist nfo/art there?

Having set an Artist Information Folder does not prevent scanning from finding artist art and NFO in the source tree, but it will look at the AIF first and only then fallback when art and NFO not found. Export no, but as I explained users can get near (if they really, really want to) by imposing the AIF structure into the source tree.

We are using export as a "cheap" media management utility to help users transition from the original limited artist stuff in source tree approach to the more versatile AIF approach. However it can be so hard to explain, and also avoid the export facility just looking too cluttered and confusing.

I see the benefits of an Artist Information Folder approach to artist art and nfo being worth this complexity:

• Allows local art and nfo for all artists, not just album artists
  
• Handles artists that have collaboration albums (with other artists)
  
• Supports having multiple music sources - an easy way to organise and access your music
  
• Liberates music from a strict artist/album folder hierarchy previously essential for local art and nfo
  
• Avoids all the "where did that wrong art come from" issues that users used to get because their music was more mixed than they realised.
  

So how does that seem to you Scott? Anything that can be improved?