Just so that, upon minimise with no other un-collapsed windows, the World gets keyboard focus (keyboard shortcuts) and taskbar appears correct...
 
In PasteUpMorph, instance side:
 
navigateVisibleWindowForward
 "Change the active window to the next visible and
 not collapsed window."
 
 self nextVisibleWindow
  ifNil: [SystemWindow passivateTopWindow]
  ifNotNil: [:m | m activate]
 

Regards, Gary