Thanks, I found the option. However, I can’t enable it when first adding a WebDAV library. I have to wait for the initial scan to finish, then turn on the option, and wait again for it to rescan the library.
Yes it’s normal, 95% of the users do not need that option, there’s no reason to have a first wizard more complex than necessary, leading to users enabling this without actually needing it and having a larger image cache than necessary.