This app could be useful for you all guys.
Use case: when we arrange all windows an our desktops (incl. external monitor) and we disconnect the monitor, it will put all windows in one screen for you. When you reconnect your monitor, all windows will stay in previous positions – will not be restored back to two monitor settings. This app stores positions of windows for you. Link to website is below, but you can also get the app from app store 10.49£.
I would really like to try this app out, but I don’t have sufficient fund for it at the moment. So if you know any good free app which does the same, please let me know.