Hi @BartH
I wrote a FAQ a couple of years ago explaining the creation and manipulation of Personal Libraries here.
It may be worth your while to read this. It may clear up a few mysteries.
Upgraded Kicad supplied Libraries are loaded into Kicad every time the program is upgraded, provided you tick the “recommended” choice when installing the program.
Personal Libraries need to be added (by you) to Kicad at every major upgrade. eg: 6 to 7 and now 7 to 8.
This is done with your “Manage Symbol/Footprint Libraries”.
If there are not too many symbols, footprints and projects involved; it may be worth remaking and relocating your personal libraries to improve their convenience.
The only drawback is symbols and footprints in your current and previous projects may have to be replaced with the same symbols and footprints from your new library locations if you start modifying old projects.
If you are interested in remaking your libraries after reading the FAQ, I’ll place some instructions here on how to easily move those libraries to new locations.