SUMMARY:

I migrated the location of my .cache, from /home/.cache to another drive, /dataHDD/.cache, afterwards Dolphin would generate file previews, but could not save them to disk -- no folder called /.cache/thumbnails existed -- resulting in Dolphin generating the preview each time a directory was visited.

Without changing any settings, manually creating /.cache/thumbnails allowed Dolphin to start saving previews to disk again in the new cache location, but this should happen automatically.



STEPS TO REPRODUCE:

1. Create a new cache location, mkdir -p /dataHDD/.cache
2. Migrate with environment variable, echo 'export XDG_CACHE_HOME="/dataHDD/.cache"' >> ~/.bashrc
3. Reboot system
4. Start Dolphin, which will now generate previews each and every time you open a directory
5. Close Dolphin, create a thumbnails directory, mkdir /dataHDD/.cache/thumbnails
6. Start Dolphin, Dolphin will now save thumbnails to disk, and load them from disk



OBSERVED RESULT:

After migrating the system cache to a new location, Dolphin cannot save thumbnail files to disk without the user first manually creating the thumbnails directory in the new cache location.



EXPECTED RESULT:

After migrating the system cache to a new location, Dolphin should create the thumbnails folder if it doesn't already exist, and be able to use it without any user input.



SOFTWARE/OS VERSIONS:

KDE Plasma Version: 6.3.6
KDE Frameworks Version: 6.13.0
Qt Version: 6.8.2
Kernel Version: 6.12.57+deb13-amd64 (64-bit)
Graphics Platform: X11
Processors: 12 × Intel® Core™ i7-8700K CPU @ 3.70GHz
Memory: 32 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 3080 Ti