I've almost finished the undo/redo. By default the UndoManager of Java has a limit of 100 undo. It seems fine for me. What about adding a new setting in the 'Game Settings' which allows the user to change this limit ?
Very good idea indeed. or an option to disable it completely. What I'm afraid of is that this could make LGM more unstable and crash faster (memory related) etc. Though it would be a good addon to LGM along with CLI.