Thanks for the link. That might be the heritage. For KiCAD, initially I believe, the s-exp parser and writer were there just for communicating with an external

Thanks for the link. That might be the heritage. For KiCAD, initially I believe, the s-exp parser and writer were there just for communicating with an external auto router (Specctra session). But it's taking over more and more. The footprints have been s-exp for a long time now. I quite like it and am experimenting with mixing in Racket for footprint editing: https://github.com/monostable/footwork https://github.com/monostable/footwork