What had me confused was that the Alnitak, Pegasus, etc. flat-boxes are part of SGP’s standard installation. I have now installed the DSD flap panel’s driver and it shows up in SGP’s flabox options.
The driver can be found here: https://deepskydad.com/store/software/ASCOM%20DSD%20FP1%20Setup%20v1.0.1.exe
Thanks for your and Pavle’s help.