Okay, did this stuff today. There's a new option that when active shows whether the item has been added to your gallery yet, on both the item info itself (at the bottom) and the on-map item label (appearing as a '!' after the item name if you haven't attached one before).
As for the schematics, there's no need for an indicator in the right-click list itself, since that list already excludes all inventory items for which you have schematics. To solve the other issue of not being sure which of your attached parts you already have schematics for, which otherwise requires either detaching parts and reconnecting or comparing against your complete schematics list, I looked at several solutions.
In the end I settled on the least intrusive option, which was to simply add a new indicator while in info visualization mode ('q'), showing a '+' in front of any part for which you have a schematic, so you have easy access to that info any time you want.
One of the more intrusive possibilities was to have special indicators appear while connected to a Scanalyzer/Terminal--a mockup:
Overkill! (And takes focus away from the hacking terminal windows, which would be less of an issue if it were just the Scanalyzer, but ideally--and arguably even more usefully--this info also needs to be available from regular terminals in case you want to indirect-hack for schematics. In this case something more subtle like the '+' is better)
