Need help with removable media collections on MacOS

I have a large collection of photos stored on an external SSD on a Mac. I have added the root folder as a collection under removable media.

As long as I first mount the disk and then start digikam, everything is working as expected. But as soon as I launch digikam without connecting the SSD first, the collection is removed from the tree. When I then mount the drive the collection becomes visible and all (11k+) photos are scanned from start. This is really annoying.

What I expected would happen is, that I can still browse all photos and thumbnails and that i only need to mount the drive if I actually need a photo to do something with it.

Can anyone explain what I am missing?