https://newatlas.com/performaxe-leg-rest-electric-guitar/55347/

When standing up, guitarists can adjust a strap to personal comfort or ergonomics. But trying to get the same feel when sitting in the studio or rehearsal room can be a challenge, with players often slouching over the instrument or tightening the strap to provide the same access to the neck that they'd get on stage. The Performaxe is a leg rest for electrics that's been designed to put frets within easy reach when seated.