How do I undo changes made in the Editor and recover deleted blocks?

To undo changes made in the Editor, click the Undo button located in the upper-right corner toolbar. You can undo up to 20 changes.

If you deleted a block and want to get it back, you can do this via Trash bin. To restore a block, go to Page Settings → Additional → Trash bin → click "See deleted blocks" and select "Recover from Trash" for the blocks you wish to recover.