You can already hide skill upgrades you bought. But I'd like to see a feature that tells you whether or not you maxed out your brain capacity cards etc. in the core stats category and hides the cards if you maxed them out. Also, the "steady on, mood loser" cards should be hideable.
And I'd love to hide the cards I wasn't able to buy (like snapshotting and unlearning) because I learned those as a skills.