If you have a keyboard that uses the Fn key to repurpose the arrow keys (e.g. Fn+Up maps to PgUp), it's irritating because the Fn key is on the left side of the keyboard so you have to use two hands. Here's a bit of #Nix config that maps Right-Ctrl in the context of those kinds of keystrokes to Fn so you can use one hand.
https://github.com/mcdonc/.nixconfig/blob/master/common.nix#L127