How to save Library path?

Hi,

I have a pocket computer (Win10 Home) with just 32 gigs, so I put everything other than "system" on disk D: which is a 128 gig microSD card that never leaves its slot.

Calibre refuses to install to D: so I have installed Calibre-Portable. That works very nicely. The Library (2 gigs, 5000 books) is in my Google Drive folder (on D: ), so it constantly syncs to the cloud, and I have a utility on each of my Android devices to sync the cloud-Library to them.

This all works very nicely if a bit slowly for the Android syncs.

But!

Calibre does not "remember" my Library path. Each time I start the program, I must "Switch/create" to the proper path. Interestingly, Calibre retains the Google Drive address in the dropdown list in the "New Location" data-entry field in the "Choose your calibre library" box.

I don't know the origin of the problem. It may be that Calibre-Portable has constraints on Library location.

It would be so very simple if I were able to install the regular Calibre program to D:. Calibre is just about the only app I have that refuses to do this.

Thanks in advance for any suggestions.