There are a number of different ways to move from one map to another. This tutorial covers a simple way to move from space to ground.
Moving from one map to the next is not the most intuitive aspect of the toolset. Nevertheless, once you understand the basics, it will make sense.
In a nutshell: When the mission objectives in the Story tab change from a space map specific objective (Ex: scan the rocks in space) to an objective on a ground map (Ex: talk to the guy on the ground), then the map transition box pops up, in between those objectives. This allows you pick the locations, contacts, etc., while specifying the exact map transitions.
So, the story tab looks like this:
talk to BO—> scan asteroids —> kill ships (all of this would happen in space)
but if you add —> Scan comps on the interior map, it changes to this:
talk to BO—> scan asteroids—> kill ships [Mission transition box] —> scan comps.
Simple Space to Ground Transition:
Step 1: Create two maps, one space and one ground.
Step 2: Add a place marker to the space map (found under ‘special’ tab). Increase the radius of the place marker to 1300, and position it near the planet. Once the player enters the radius of the marker, it will prompt a beam down (after we include the mission objective). Also, adjust the spawn point to face the place marker, outside of its radius.
Step 3: Add a NPC contact on the ground, in front of the spawn point on the ground.
Step 4: Make the first mission objective ‘Reach Marker,’ and specify the place marker in space.
Step 5: Make the second mission objective ‘Talk to Contact,’ and specify the contact that you put on the ground.
This should cause the map transition box to appear between the two objectives.
As you can see, we used a contact to move from one map to another. This is not the only way, of course. Experiment with scanning objects, other reach markers, and spawning enemies.
I hope this helps.