[oyvindo]

But also note that Isenguard does not trim names, so I fear "Michael Jackson; Diana Ross" with separator ";" will result in artists "Michael Jackson", " Diana Ross" (note the leading space).

I guess I just have to rebuild the whole library then. Is there anywhere a command within Kodi to clear and rescan without physically deleting (removing) the library?

So I deleted the library from the NAS, uninstalled and reinstalled Kodi, replaced advancedsettings.xml with this one (the bold is my modification):

<advancedsettings>
<videoscreen>
<screen>0</screen>
</videoscreen>
<!-- <cputempcommand>sed -e 's/000$/ C/' /sys/class/hwmon/hwmon0/device/temp1_input</cputempcommand> -->
<cputempcommand>/opt/kodi/bin/get_NAS_temperature.sh</cputempcommand>
<gputempcommand>sed -e 's/000$/ C/' /sys/class/hwmon/hwmon0/device/temp1_input</gputempcommand>
<jsonrpc>
<compactoutput>false</compactoutput>
<tcpport>9091</tcpport>
</jsonrpc>
<musiclibrary>
<itemseparator>; </itemseparator>
</musiclibrary>
</advancedsettings>

Then I rescanned the the whole library with all scrapers disabled.
Still, Kodi refuses to accept semicolon+space as separator.

"Michael Jackson; Diana Ross" comes up as a single artist named "Michael Jackson/Diana Ross" (Just like AC/DC).

I'm stuck now. Need some good advice.