[basd]

If you use the default storage location ...

Thanks, this is good information. I do appreciate your offer to take a look at my files.  What email would I share to?

No, actually I do not use the default location, because I want easy access to the song files from other applications. But, of course, the library.db files stay in the default location.

I think one option for me (to solve the OneDrive update synchronization) would be to rebuild the entire default database, but I already have a gazillion hours in this project (setting up multiple computers, rewriting a lot of pdfs into cho files, etc.) So, at present I can make it work, it's just "not elegant" -- because it unnecessarily uploads all of the unchanged song folders and song files.

For the additional libraries, I made sub-folders in OneDrive, but this results in saving multiple copies of the songs that are also in the main set of files.  So, a solution that involves just copying the library.db files would be more efficient. It also would allow me to utilize my NextCloud system instead of OneDrive.

So, I am going to see if I can implement library.db copying system. Then, if the storage location is in OneDrive, the song folders/files are always synchronized and all I have to do is copy the libraries. 

I tried copying mobilesheets.db to OneDrive, but without the hash file, the synchronization system does not "see" the db file.

I'll let you know how I do on this.

Now if I could only figure out how to make MobileSheets run on Linux ...