Hi All,
I was having a terrible time in getting custom maps to show up in entrenchment but was able to put a few other posts together and figure it out. For others that are having the same problem here is what I did.
1) Save the custom map in the Galaxy folder in the game directory
2) In the Entrenchment folder (Within the Sins of the solar empire folder) look for a file called "galaxy.manifest"
3) Open up this file, scroll to the bottom and add the map name you wish to add . Example : fileName "Jim's Universe"
4) Scroll to the top of the file and change the filecount= number to include the map you just added.
5) Save
That should be it. Worked great for me but was unable to find any one post that clearly stated on how to get the game to see the new map.
Hope this helps.