Double-click the caption (the title bar) to enter compact mode. The window shrinks to the caption and a launch field, and it is not resizable. Double-click the caption again, or press Esc, to restore the previous size.

The field starts empty. After you type, it lists installed Start menu programs and executables on %PATH%. A Start menu shortcut and the same .exe are one row. Enter launches the selected program and leaves compact mode open.