Few minor changes could be done to the interface editor to make life easier for people working on interfaces.
The dividers between the macro, menu, and window lists should be movable to resize the lists, or the window list height should be increased greatly. Doubt people have very many macros and menus, but, who knows.
When you have a window selected and press delete on your keyboard, you get no warning and the window goes poof. An "are you sure?" alert would be nice before deleting.
When you open a window to edit it, the window automatically goes to the top left corner, which is extremely annoying since when the window is shown at runtime, it appears where you saved it in the editor and having to move it back to a spot you want it in every time you edit the window is a pain. Either saving the position or centering it when you open the window to edit it would be nice.
The layout controls window should go up and down on the left side of the screen. It's like right in the way every time you edit a window (especially with the window resetting position like mentioned above).