I want to create a scenario where a custom poi is in a large mountain. And has many basements that run deep into the mountain. So first question. Can I use the planet that I have the poi built as the scenario? If not, can my POI be placed into a mountain and it have hallways and etc cleared of terrain? Or would we have to manually clear terrain?
You can place a poi in a mountain system the issue will be where the door is. Depending upon how the poi entrance works you may need to have a fixed location for the poi on an fixed seed world or it wouldn't be consistent
Placing POIs on mountains can also be tricky. It will depend on the type of mountain. The mountain will need some flatter areas it can spawn the POI otherwise it will cut into the mountain and not look very good.