Create blank mission.
Drag two groups of soldiers on the map.
Select both groups (and soldiers).
Save that as custom composition named Whatever. (name doesn't matter)
Open new blank mission.
Drag Whatever from custom compositions to mission.
Behavior - layer Whatever will be created with only Alpha 1-1 group in it. Alpha 1-2 will be in root layer. In the lobby, Alpha 1-2 will appear before Alpha 1-1.