The Show Known Techprints Mod adds a new icon next to all techprints to indicate if the techprint has been applied or not. No more will you buy duplicate techprints or sell the ones you need without realising!
Hovering over the new icon will also tell you what you will unlock by researching and how many tech prints are required.
This mod has been created by me, SpaceMoth! A mod I made after passing on yet another Techprint sale due to not knowing what ones were needed or not.
This mod is available on GitHub with the GNU GPL v3 License so please feel free to take a look to help develop your own mods!