Renaming the page does not change the page ID, which is what the system checks when adding Addon content to avoid adding doubles of everything. Depending on what's changed, you can copy tokens/etc to a new temporary page, delete the page, then bring them back to the new map. Also, there is no Undo button, but CTRL-Z does work in the VTT! So if you notice you deleted the wrong item, you can get back to it quickly with that shortcut. I hope that helps!