That’s great @TrevorG. A new Raspbian release was just put out today but there’s no sign of USB boot so that’s probably the only USB option on the Pi4 for a while.
There’s a tutorial included with the images called transfering modules with WinSCP. That’s probably the best way to back up modules to a PC to be transfered again. The other option is to make a clone the drive using something like win32disk imager and then open the image file with 7zip. Once inside 7zip there are two files, open the bigger one and you should be able to browse the file system to /var/www/modules and just drag those out to your desktop.
@giakonda has a tutorial on his site about migrating Kolibri data. I’ll try and find the link again.