Resizing window offscreen
You can usually just move a window to the bottom of the screen and then resize it by dragging the top edge up.

These commands don't usually resize windows so that they are outside screens:


tell application "SomeApp" to set bounds of window 1 to {0, 0, 9999, 9999}
tell application "SomeApp" to set size of window 1 to {9999, 9999}
tell application "System Events" to tell process "SomeApp" to set size of window 1 to {9999, 9999}