Some sort of option to lock anchor settings on controls (a little button next to the auto-anchor one) would be very useful. Several times now I have setup a window, anchors and all, then went back needing to make the window bigger or smaller, to insert new controls for example. This basically requires you to go through every control on the window, unset its anchors, re-size the window, then go through them all again to reset the anchors.
EDIT: Maybe a button to match anchors would be a better idea. Like we can do with width and height.