Can I finally Ctrl+s jpeg image? And no, export is not enough because first time it will ask for for path and compression level which it already knows. I just want to Ctrl+s and be done.
Almost all programs treat the “Save” operation as something used with the native format, in this case XCF files. These preserve things like layers, etc. JPG and other formats are exports because after you close the file you can’t get all that stuff back when you reopen it.
File - Overwrite file, that's been there for a while. It can be turned into a hotkey, it's unmapped by default, and I don't think that'd change nor should it change, given how user hostile that'd be, the long history of how it works in editors like that, and with how they lean towards non-destructiveness of it all. Also, that just sounds like perhaps a simpler editor would be a better fit, like Paint.
It seems like you can assign this action to Ctrl + S, yes. See here:
I think this would be awful default behaviour, but I guess it’s nice to have the option if you really want it, and I was pleasantly surprised at how easy it was to find after reading your comment.