You could consider window cling film. It’s not permanent and can be repositioned.
It goes up with soapy water and peels off without damaging the windows.
I’ve used it in my office and the bathroom windows for privacy without compromising the light.
It may not suit your needs if you’re looking for something to block out light.
There’s hundreds of patterns and options.
This is what I purchased and when the light hits it, it becomes iridescent and quite pretty.
https://www.amazon.com/dp/B01N20YR6B...w%2Bcling&th=1