When you change an element property from the element properties dialog or from the docking pane you can not cancel it. So you must invalidate your changes yourself. It is not very easy to remember what you have modified. So if you can include this modification in the undo / redo functionality, it will be easier to come back on properties changes. Perhaps it will be interesting to have an history dialog of all changes on all (element, reports, queries).
Thanks for all.