Describe the feature

There is room for improvement with our current app bar. Here are some things we should consider:

• Disable the back button when it is not relevant
• Improve the app chooser styling
• Possibly center the app chooser or move it to a button in the overflow menu (maybe only on mobile)
• Move it into the system title bar area
• Support contextual app bars that focus more on the title / other info than a big search bar
• Add the app and/or user icon
• Add an option to disable the app bar (add DisableAppBar option #1072)

If anyone else has ideas or feedback here, that would be helpful.

Relevant code

No response