..\Steam\steamapps\workshop\content\32470\1125571106\Data\XML\Conquests\FTGU

Edit the Caimpaigns_FTGU.xml with an editor like notepad++

Search for this string: <Campaign Name="Sandbox_FTGU_Empire">
then you are in the section for the Empire, where you can change your starting forces

But i cannnot select a World Devastator as Statring Forces. Does anyone know the Reason?

Take a look in the units_capitals.xml ;-)

Change, for example, the following string:

<Starting_Forces> Empire, Carida, Lancer_Frigate </Starting_Forces>

with this:

<Starting_Forces> Empire, Carida, World_Devastator_Capital </Starting_Forces>

or add the above line.

thanks it works now. I needed the correct Writing for the World Devastator

Hey, how would I do the same for a normal Full Galaxy GC?