CurseForge Link
https://www.curseforge.com/minecraft/mc-mods/personality

Mod description
"Adds more livelihood to players by introducing some new actions and animations. These include keybinds for sitting and crawling, as well as an animation for climbing. More will come in the future." - from mod page

Why would you like the mod added?
It is a good quality of life and role playing addition for multiplayer servers. You don't need to place a trapdoor anymore to make you crawl (which is absolutely senseless haha) and the sitting feature is good for roleplaying (for exampe sitting on a couch created with chisels & bits).

I'd suggest to change the default keybindings. (e. g. use [Numpad Arrow Down (Number 2)] for Sitting since you won't use the sitting feature that much so that the location of that key bind might be away from the rest)