One of the (many) things I like about Artrage is the ability to define, with some ease, individual short cut keys. I have defined many!

I use the References scrap for colour mixing and I regularly make mistakes. I know that there is an 'Undo' key but I make so many mistakes that I wondered if there was a designated shortcut key to 'Undo' in scrap, or if it is possible to define one?