how can I save the app's every widget, list item added and changed by the user while using the app so that when he/she opens it it's still back to how he/she left it? I'm new to Kivy ,I would really appreciate help, thanks!
When the app is paused or closed (in the on_pause and on_stop methods of your App class), write code to save whatever app state you want. You will need to serialise it somehow, e.g. as json.
When the app is opened (in the build method of your App class), write code to read that file and reconstruct whatever gui state you wanted from it.
How do i save the state of my app? kivy/kivyMD