Hang a water repellent curtain on a straight rod over the entire window area, so it can be moved to the side when not needed, or hang a hinged, waterproof frame above the window, to be lowered when needed.
Paint if with a Paint By Numbers Kit.
hang shower curtain over it, or remove & glass block it
If your concern is privacy, simply cover the glass with privacy window film. They come in various colors and patterns. Here's a simple plain frosted design:
Or you can look at the colorful " stained glass look alike " ones also available.
When I was confronted with this problem, I hung a tension shower curtain rod and put a vinyl shower curtain there, but I carefully cut the shower curtain shorter, so it would not bother someone taking a bath in the tub--it could just be pushed into the far corner, but didn't hang down below the top edge of the tub.
The shower curtain was necessary because the window frame was wood, and the paint constantly peeled due to all the water hitting it.
thank you all for your clever ideas