Most of the actions you perform in Bookdog are recorded and piled on to an undo stack. To undo what you have done, click the menu Edit > Undo. With each such click, your actions will be undone, in reversed order of their initial performance. The menu will show you the last action which can be undone.
After you have undone action(s), you may Redo the actions. The Redo menu item operates on a redo stack which works the same as the undo stack.
Undo/Redo action availability Because Bookdog allows you to move items between browser windows, Bookdog has only a single undo stack and redo stack, so all of your undo and redo actions are always available, regardless of which window is frontmost. However, once you click Save, Revert, or Close a Main Window, all pending Undo and Redo actions for all documents are forgotten. The logic is that you can't give back or re-take things from documents that are no longer available.