1. To undo or redo changes made in a design, make sure that no items are currently selected. This can be done by clicking outside the canvas or pressing the esc button on your keyboard.

2. Two curved arrows will appear in the bottom left corner of the canvas with numbers beneath them. The top arrow, pointing backwards, is the undo button. The bottom arrow is the redo button. 

3. Click the undo button if you want to undo any change you've made to the design. You can click this button to undo every change you've made from the beginning of your design editing session--the amount of edits available for undo-ing are the numbers listed beneath the arrow. 

4. If you accidentally undo one too many changes or if you just want to go back and forth to make design decisions, clicking the redo button can redo anything you recently undid, in the reverse order (the most recently undone change will be the first one to be redone).

Notes: 

The redo button can only function if you have used the undo button first.

Pressing "ctrl + z" is a shortcut to undo a change made to the design, however, it only undoes the singular, most recent change.