Undo/Redo
Code Editor contains a stack to track all modifications to the text file.
You can undo or redo any modification in sequence. There is no limit for undo/redo stack, you can undo/redo as many steps as you need.
Undo
You can click Edit->Undo from toolbar to undo the last modification.
Redo
The undo-able modification can also redo. You can click Edit->Redo from toolbar to redo the last modification which undo previously.