below the habitat section ( between the towers and the fuel tanks ) - you can see several straight extensions. - the system modders can place vanilla docking ports on the end of them.
the whole thing is probably a huge pain to hitbox ( i d probably suggest only a very rough hitbox ) - and docking ports need to be quite far away from it - or larger ships get stuck in it - like they get stuck in many asteroid bases.
when docking is a problem - i might also extend the corridors a bit more - so that docking happens quite "far" from the station - like ... docking points are 2k away from the main structure.