I found myself desiring the ability to combine different tab types (standard, private, Tor) in the same window.
Example: I have ProtonMail as a pinned tab in my main browser window. As Proton has an .onion site, it would be nice to have the .onion site open in a Tor tab pinned in my main browser window while other tabs are standard, private, or Tor tabs. They could be differentiated by background color as the different windows are currently.
Just a thought.