If you click on the button "Page", a pop-up menu will appear:
Click on "Undo" to undo the last change that you made. Version 3.0 will store the last 10 changes that you have made, and you will be able to undo those last 10 changes. Please keep in mind that not all changes or actions can be undone - for example, deleting components or deleting pages cannot be reversed. If a process or action cannot be reversed, you will be informed that continuing is irreversible.