Relocating temp files for Garmin Express...

So I have a shiny new Fenix 6x and I want to update maps... but I need 18gb of disk space... I HAVE probably 150GB of free space, plus a number of USB drives offering a multiple thereof, but I only have 10GB of disk-space on my C: drive... and Garmin Express doesn't let me change where it saves temp files...

For now, I have done a brute-force file relocation with directories I will copy back when I've finished, but is there really no way to reconfigure Garmin Express to store things on one of the many drives I have where the space is available?