Keeping track of what changes can save you lots of frustration. In Rem's Studio, you can press Control + Z to undo a step, and Control + Shift + Z to redo it.
If you want to undo a lot of steps, open the history viewer by pressing Control + H, where you can see the most recent changes in a list.
Created: 20:38, 21. Dec 2020; Most recent change: 13:02, 26. Jan 2021