I’m in 1.02 and started a new game, just doing R&D.
At the start (before doing any R&D) you can press the plus on an items and see it’s sub parts greyed out.
Once you research the first one the greyed out parts become white and usable, but the next tier doesn’t become visible/greyed out (the plus is deactivated).
not sure which way this is supposed to work, but presume it’s supposed to be consistent.
I will check and update on other sub slots but found a diff bug while typing this .