Whilst I didn't get the "persistent temp files" either and I still don't know what the use-case is beyond persisting unnamed buffers and I don't understand what the reason for saving unnamed buffers is, if its unnamed how do I know whats in it to switch to it when they are all named "Untitled"?
They will get some file name (see the screencast, I personally would suggest names `scribble_1`, `scribble_2`, etc.)
So I can't suggest anything better than the descriptive "save unnamed buffers".
That's not the whole thing the patch does though - it really is some "scribble mode" with additional features: 1. On opening an unnamed buffer, it saves the file (same as instant save) 2. It auto-saves this buffer in user-specified intervals so the user doesn't have to care about saving it 3. When you close the buffer, you are asked if you really want to close it - when you do, the underlying file is deleted so, again, you don't have to care about files here. When you select that you don't want to close it, the open buffer is preserved - with a slight limitation. The limitation is that plugins can't interrupt file closing so what the plugin does it that it reopens the underlying file after it's closed (and of course it doesn't delete it in this case) - since this only happens when the user makes a mistake and tries to close the file by accident, I think it's fine to have it implemented this way. 4. When you use "Save as", the underlying "scribble" file is deleted automatically and only the file under which you saved it is preserved.
Now to why people (https://github.com/geany/geany/issues/905), including me, want to have this feature - the Scribble panel is extremely limited and the basic editor features don't work there (see https://github.com/geany/geany/issues/3558). Having a full-blown Scintilla editor used for Scribble with all editing options and syntax highlighting in a big window would be really nice. And this PR is quite a nice way how to implement it in a pretty much invisible and care-free way for users.