We lock our shower door when traveling and used to keep the door closed when not being used when parked.
With the door closed , it seemed to me that on hot days the temps inside the shower area are quite warm and after using the shower the humidity lingers in there.
Our shower uses a long magnetic strip the whole length of the door to lightly hold it closed.
If I put a block in the doorway, it would hold the door open a bit, but if the coach is tilted a bit, the door will slowly swing open. And if make a temporary latch to keep door open only an inch or so, when I want into the shower, I found I yanked the temporary latch because I forgot it was in place.
I found a simple solution that holds shower door open enough to let it ventilate, keeps door from swinging when not level, and does not interfere with pulling door open.
Magnets that lightly attach to both shower frame and door to keep door open, yet not swing. Solution is not perfect, but is working for now. Lowes had packages of small (7/8" x 1/4") magnets that I stacked to give us the right spacing, yet not be too heavy. Currently using 8 magnets that stick to each other, but I taped them so they stay together when dropped.