It is possible to show a progress indicator for the download of an addressable, i'm using addressable, but naninovel loads the resources automatically and I would like to be able to show the user some download indicator.

I'm not aware if there is a hook in addressables API for the progress outside of individual operations (in which case use that), but otherwise you can override Naninovel's addressable resource provider to access each download operation it starts and get the progress.