⌘Z: Undo (same as clicking the Undo link that appears after deleting an element)
⌘⇧A: + Add
These have been set to work in Google Chrome and if the URL
Bonus: Also included is a macro that clicks the Save button automatically every 1 minute. This could get annoying and so it has been disabled. You may change the save frequency and enable it if you want.
Install Keyboard Maestro.
Import the macros by either double clicking on the .kmmacros file or by going to File > Import Macros Safely… and selecting the macro file in the Keyboard Maestro Editor.
Click the “Oxygen Group Essentials” group name and tick “Enable Macro Group”. Make sure “Disabled on this Mac” is not ticked.