I have a two monitor setup on my computer. What I do is open firefox, load a second tab, and then move that tab to my second screen so that I have Firefox open on both. However, if I were to move a tab to my other monitor while Discord is open on that screen, then the tab doesn't load into another window of Firefox and would instead reappear back to the original window. I would have to minimize Discord to get it out of the way before moving the tab to the other monitor and turn it into a secondary browser window.