Implement header bar
Header bars are a cornerstone of the GNOME HIG, and Terminal is one of the last core apps that hasn't adopted them. It's become a problem to the point where downstream distributions are shipping Tilix instead of GNOME Terminal for this very reason. We badly need to align Terminal's design with the rest of the platform.
Here's a mockup for what Terminal could look like with a header bar:
Let's make this happen, it's time :)