How to have GOG launches SMAC-X ?

There should be two executables in your installation folder; terran.exe opens vanilla SMAC, and terranx.exe allows you to play Alien Croosfire.

If you are using Galaxy, instead of "Play" click "More" and look for the expansion (Galaxy, by default, launches the vanilla game).

Ah indeed, in a sub sub menu, you get the option most if not all players will want! Not very user friendly... But oh well it works at least.

I'm surprised you are locked in full screen mode and alt tab does not work nor changing virtual desktop in W10, any idea?

Thanks anyway, much appreciated!

I'm using Galaxy and I'm not seeing any More button...strange.

Guessing you have Galaxy 2.x which no longer has "more" it now looks like a couple lines to the right of "Play" (see attached). This threw me off after the update.