[wibbily]

Poorly, usually. Markdown files everywhere, occasionally a google doc if I'm away from the laptop. Usually hardware projects will end up in a git repo, but mostly for the benefit of whatever firmware I'm writing around it - if there's any specific Kicad integration with version control, I wouldn't know.

The biggest changes I've made recently are leaving notes inside the schematic (so I can't miss them) and keeping local copies of every datasheet and app note that I need.

[warble]

Kicad stores as XML as you probably know and is fairly human readable, so I use git on the project folder directly. Works great, although manual merges are a little involved, but I'm never in that position.

Also a lot of notes in the schematics/layout as well, utilizing layers. Overall I'm pretty satisfied.