That doesn’t make a lot of sense. The T could only be there when the S is also there. I think what you’re going for would look more like

(s/t)he(y)

Or maybe

(s)(t)he(y)

(s)he

✨they✨

Used to be big on sleeping on my back but recently I can only fall asleep when in my back

Edit: looks like I was having a stroke when writing this originally. I wanted to say I can only fall asleep when on my stomach now