I know it takes some time for drivers to reach the rescue media, but, is there a chance of supporting Thunderbolt 3 external drives for restoration files? I have a Thunderbolt 3 m.2 NVRM external drive and backups are very fost, but don't appear when booted from the Macrium Reflect Windows Boot Menu item.

I have updated to the latest Windows Boot Menu rescue file.

The WinPE/RE kernel itself would need to support Thunderbolt overall before drivers for any given Thunderbolt device would be useful, and I’m not sure that it does. Typically a storage device doesn’t require drivers itself anyway beyond the built-in generic storage device support within Windows, so if you don’t see the device, then it’s probably Thunderbolt support that’s missing. That was built into Windows as of Win10 1709 or thereabouts.

A similar example is Bluetooth. It isn’t possible to use Bluetooth devices in Rescue regardless of any drivers you may have because WinPE/RE doesn’t have a Bluetooth stack to begin with. (Separately, the fact that Bluetooth pairings are stored in the OS means that switching a device between full Windows and Rescue would be annoying, and that may be why Bluetooth support isn’t implemented, but that’s in addition to the technical limitation here.)