For commands, you can type
/help into chat to get a list of (some) commands
I’m not sure how much I can do for sitting if I’m going to be honest, but I’ll give it some thought. I might be able to make a player animation editor. This would allow the dev to make a sitting, jumping, crouching, etc. animation. You could also apply buffs/debuffs to each (sitting could regen stamina faster, but movement is set to 0).
I do want to say I don’t know how feasible the player animation editor (or whatever I call it) will be, and I’m not sure I’ll have the time to make it, but I definitely will give it some thought, just realize I’m not a miracle worker