WP Page Builder has unlimited undo/redo options with a single click.
Website building requires a lot of trial and error process. So having unlimited chances at undo/redo actions is a necessary part of the page building plugin.
At the bottom of every page, you will see the above two arrows. The left arrow is for the undo option. The right one is the redo.
Every time you make a change you can undo with just one click. If you want to go back to the prior state, just click on the right arrow of the redo and you will have the website in the last changed version.