I know it's a lot of work, but are you planning a multi-level undo/redo? It can make editing mistakes a lot easier.
Even nicer would be photoshop style undo/redo + "step backward". Confuses the metaphor a little if you aren't sure exactly how it works, but worth it in my opinion.
I agree. As far as I'm concerned, multi-level undo is essential. I work very quickly and sometimes realise I've done something stupid two or three steps down the line. A history panel would be really nice if possible, but a bit of a luxury item admittedly - not strictly necessary!
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