I have an external monitor connected to my MBP via HDMI. I can use my laptop in 'clamshell' mode, where I close the laptop's lid and work off of my external monitor.
The problem I have is that when I open the laptop's lid some of my windows move off the external monitor to the laptop. Some trial and error shows that if a window is on the laptop when I close the lid, that window will reappear on the laptop if I reopen the lid, even if I move the window around while it is on the external monitor.
How can I prevent my mac from moving windows to the laptop. I want all windows to stay on the external monitor until I physically move them to the laptop, and once I close the lid they should stay on the external monitor even if I re-open the lid.