Mods that do things you would have never thought to look for on your own, but which now that you have them, you couldn't go without them

Title says it all, but perhaps it requires some more explanation.

Donald Rumsfeld once said that there are three types of knowledge: Known knowns (Things that we know we know), Known unknowns (Things we know we don't know), and Unknown unknowns (Things we have never even considered before). Slavoj Žižek later added a fourth category: Unknown knowns, or unchallenged assumptions we have not realized we have made. The Persian poet Ibn Yamin also came up with this set of distinctions several centuries before them.

This post is about the third category, and perhaps also the fourth. Those blind spots in our world which we are completely ignorant of, or those parts of the universe we have seemingly assumed are immutable, but are in fact as malleable as any other.

I think an apex example of this is the "Security Overhaul" series by powerofthree et al. No one has ever thought to themself, "Man, I wish there were more models of locks in Skyrim's lockpicking minigame for all the different types of doors and chests in the world.". Probably not even the mod authors themselves; like it only exists because one of them was told the idea by their future self in a time loop. Despite this, I'd say this set of mods is almost an objective improvement to the game. It simply Does Not Make Sense for every single lock in Skyrim to be completely identical like that.

To elaborate on how this "Rumsfeld matrix" applies to Skyrim mods (At least, how I'm using it here)... A mod you know about is a known known. A mod you don't know about, but do know about its general category or know that mods like it exist (Mods that add followers with a dozen hundred spoken lines, or hours-long epic quests) are known unknowns. A mod that does something you've never even heard of before is an unknown unknown. A mod that does something you never realized there was a mod for, but which you do understand the general concept of (Perhaps that you mistakenly thought was part of the vanilla game, or that no mods of it do/can exist), is an unknown known.

Since the instruction "Tell me something that you don't know that you don't know" is obviously impossible, I'll also explain that that's not what this is asking. More like, what is something that to you previously was an unknown unknown, but is now a known known? Or that you predict is an unknown unknown to me or most other people reading this thread?