When I have my computer plugged into an external monitor, I want new browser windows to open on the external monitor, but they always open on the computer's monitor. I have gone through the entire process at https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems (clearing cache etc., trying safe mode, creating a new profile, refreshing Firefox, reinstalling Firefox) and the problem persists. This happens if I manually select "New Tab," "New Window," or "New Private Window" from the File menu with no existing windows open. It also happens if I use the key commands for any of these menu items. It happens if I use the menu bar on the computer's monitor or the menu bar on the external monitor. Opening a window and dragging it from the computer's monitor to the external monitor does not change anything. I've also tried using Divvy (https://mizage.com/divvy/) to move the browser window between windows with a key command, but after moving it this way nothing changes—new windows continue to open on the computer's monitor. How do I set which monitor Firefox will use for displaying new windows and/or get it to remember my preference? System details: MacBook Pro (15-inch, Late 2016) macOS Catalina, Version 10.15.2 Firefox 72.0.2 LG HDR 4K external monitor (Model 27UK850) CalDigit TS3 Plus Thunderbolt dock Computer connected to the dock with Thunderbolt 3 LG external monitor connected to the dock with DisplayPort 1.2