Is there a way to make a window exclusive for a tab so that no other tabs are open in that particular window (and perhaps the tab bar is hidden)? Or is there to designate one of the windows as the "main" window?

I use two Firefox windows: one that has the web interface of my music player only, and another window for other internet browsing. However, sometimes when I open a link from outside Firefox it opens in the window of the music player rather than in my "browsing" window. Moreover, when I switch to Firefox (using Cmd+tab on MacOS), the music window is selected rather than my "browsing" window, even if the last selected window was my browsing one. Is there a way to make a window exclusive for a tab so that no other tabs are open in that particular window (and perhaps the tab bar is hidden)? Or is there to designate one of the windows as the "main" window?