The body has its own momory. It knows that the fireplace is hot of that a stone is heavy. Te mind and experiance showed the body that long ago. So You don't need to think about that any more. Peeing in bed is just like that. Your boby Does not pee when you lie down.
If you want to pee in bed it is a good suggestion to first train yourself to pee whie you lie down.
Here is my way to teach the body to start peeing while lieing down.
Start to pee next to your bed and then quickly lie down as the stream flows.
Keep relaxed. After doing this several times the body learns that peeing in that position is OK.
When you refind you capability to pee lieing down, try to lie down every time you pee.
Now your body is ready for sugestions of the mind to become a bedwetter.
It worked miricals for me.