That is an excellent solution that worked great. It led me down through a rabbit hole of possibilities that led to something less elegant, but without the extra copy step.
Music Bee does not look at GUIDs for drives; it only uses the drive letter. Last time I setup static drive letters I ended up with several different schemes over a few months using it. The first few would be fine, but I would forget what I did when I would try to add another drive after a few weeks or months. I got frustrated and switched to streaming. Some of my music is just not available to stream, no single service has everything I like, and I was missing some of my favorites. I figured I'd take another jab at it.
I broke into MusicBee3Settings.ini and created a <DeviceSettings> block for each drive letter from G through Z with the base settings I want. Now it doesn't matter what letter the device uses, the basic settings are the same and I can concentrate on what music to put on it. If I don't try to customize settings, I should be all set.
Edit to add; I still don't have a fix for the error I get if the base folder doesn't exist, but that's minor.
Dell Inspiron, i5, 16GB, 256GBSSD
Windows 11 Preview
MusicBee 3.5.8447, standard install on C:\
Library on External drive;
293,621 Tracks, 18,393 Albums, 4461.93GB, 850d 12:20
Topping D10 32bit 384 kHz USB DAC
O2 Headphone Amplifier
beyerdynamic DT770M 80 ohm
Crossfade M-100 Master Over-Ear