The read-only mode switch affects how movies interact with savestates after you start a movie playback and load a savestate. When you are in read-only mode, the movie will resume playing from the loaded savestate. When you are in read+write mode however, your input will be recorded over the original movie ('rerecording'). If you wish to start rerecording immediately, you should switch to R+W mode, save a state and then load it.
To make this more user-friendly, I also added a unique ID to the movies, which allows each movie to have an individual set of savestate slots (plus another set for when not doing any movies). This is as recommended by staff at TASVideos.
10 slots are offered along with 'Save to Oldest Slot' and 'Load from Newest Slot'.
The savestate format is similar to the movie file format. It is called CST (Citra SavesTate), and is basically a 0x100 byte header (consisting of magic, revision, creation time and title ID) followed by Zstd compressed raw savestate data.
The savestate files are saved to the `states` folder in Citra's user folder. The files are named like `<Title ID>.<Slot ID>.cst`.
