is
located on the title bar to the left of the frame window 'Minimize'
control.
When pushed with the LMB, it resizes the FS/2 window to a small Swap
window. The Swap control is
located on the title bar to the left of the frame window 'Minimize'
control.
When pushed with the LMB, it resizes the FS/2 window to a small Swap
window.
The control button changes shape depending on its current state.
When in
swap mode 
,
it may be used to restore the normal frame window.