I had a similar but different situation. The first time I installed seafile client and it prompted me for a new seafile directory I, of course, didn’t understand how it was going to work, so I set the directory to somewhere nested under my Documents folder for testing (the rational being that I wanted to put a subset of documents in it). Later when I wanted to add my whole documents folder, seafile server kept refusing to let me with an obscure (to me) message about a library not being allowed to contain the system directory, or something like that. I had by that time actually forgotten about the folder installed down there, as I did not use the default library that was also under there. Finally tracked it all down… and figured out it worked and how to move it. And so, at long last, I come to my advice for you!
You’ll find the .seafile-data directory location defined in /home/(user)/.ccnet/seafile.ini
I imagine you could just change that definition, but I haven’t actually tried it. Let us know! I didn’t figure out where that setting was located until after I got frustrated and wiped out my seafile client installation and reinstalled just to move that directory. If you use this method then when you install just choose something like /home/(user)/.seafile-default under which the .seafile-data will then be created. Your default location for libraries will be there also, but you can override that when chosing sync directories.
Seafile has confusing amount of places for config files. I found: ~/.ccnet/, ~/.config/Seafile/, and also “~/.config/Seafile Clientrc”. And of course (wherever)/.seafile-data/
I had already found the .ini file but got in a mess when trying to use it to move the .seafile-data dir. I had planned a few more experiments but then your message gave me a simpler idea.
I removed the client completely and reinstalled. Then on the 1st login I specified to use folder: /home/(user)/.seafile-config as its base folder. I had to create it 1st of course. Then the client stuck its config files in there out of the way. Simple and easy to replicate on other clients.