Save/Restore app state

I'm sorry, I don't really have the bandwidth for this at the moment - but what you're doing there (basically just changing jsfNameFromString(SAVED_CODE_VARIMAGE) to something else) looks fine to me, so there might just be some small bug in what's been done. Maybe print the filename to the console and check?

I'm not sure your persist argument is super helpful though.

In theory, yes, I'd be up for merging a PR that allowed you to save to image files (maybe not the timestamp/graphics/bit though). Ideally the changes in src/jsinteractive.c would be a bit cleaner though as there looks like a lot of code/duplication in there