Hi Jack, undo is located on the bottom toolbar, right next to "Save". I've tried to put some of the most frequently used buttons in this area so that they are always visible and available. Stuff on the right-side palettes may not be immediately visible if you have activated some other palette in the same row.

You can also use the keyboard shortcut Control + Z to do an undo as well.

I have thought a little bit about possibly moving the undo, redo, and delete buttons into the Edit toolbox where you expected them. But that would start to make Edit kind of a bit large and overbearing...

- Michael