The do something like this. Pretty much the horse bit lays down in a position where the humanoid bits can access whatever. They'd be sitting on the floor mostly unless the place they're at has cushions of some sort.
Damn codecat that pic...but funny thing. On bendy it's typical 4 leg taur but on non-bendy it seems it's a leithan (I mean it looks we see one side legs only and...there is 3 of them so...6 in total ^^)
As for OP question using Wsan pic me think bendy is how their sit and non-bendy way looks like position to sleep. Just how their then put their upper part that can be itneresting to think about since their not have merely neck and head there but whole waist up part of body ^^
Has it been stated anywhere that leithans have stiff spines? I was under the assumption otherwise. Sitting would probably be laying down, what with 6 legs, but it wouldn't be impossible to have the front two erect.