So, after removing all the CRYPTED files (12GB),

joplin-desktop is now 44.6GB (as expected, decreased by 12GB)

So most of the data 37.1GB out the 44.6 in a folder name 'profile-9utt9gea' :

Apparently the profile I am using (with Joplin Cloud) is a second profile. It's the one with "id" : 9utt9gea

I am not using the first (default) profile - I had actually forgotten about it, since I used it just to try out when I started using Joplin. As those tryouts were with OneDrive, I hadn't thought they were also using space on my local SSD.

I'd like to remove that old profile. Unfortunately it's the default one. I could find the procedure to delete an additional profile, but not the default one, see link below