I'm sorry, I can't presently figure this out. I'm able to create the two GmxGen and GmlCppExtFuncs with the terminal no problem (once I figured out what was going on with that side..) Everything I did with Visual Studios was uh... Miserable. I still can't figure it out (lol :/) and this might be where I'm stuck, if anything. My best guess/hope was that from the V3 github page, it was going to build all the scripts into some .dll or .so files so that it could be imported to the GM Extension, but... You know, didn't make it that far. (And I probably am on the wrong track, anyway.)
I suppose for the time being, I can default to the Steam Proton and Windows variation to use Lua (I think with the 2.3 scripts?) And if GMS Linux ever leaves Beta, hopefully it'll be able to make use of the .so files; I'm assuming it's the beta that's at fault and not able to make use of the .so files, anyway. (So, thanks for taking time to help, I appreciate it!)