I have spent a few hours yesterday trying to figure out how to add new types of modules to my ship. How to add a new module type to your ship in Starfield:
What I could not figure out for the life of me (and yes, I watched 5-6 ship building tip videos on YouTube) was:
How do you add a brand new module type to your ship?
Go to ship builder mode (X) and move the focus away from your ship (so nothing is selected) and then press A.