[FR] Hide sources from element index when only one

[ZapaNOR]

I really like the new option in Craft 5.9 to create custom sources and have them in the sidebar in the control panel.
One thing I personally would like to see some time in the future is the ability to hide the source list (is that the name?) when there is only one.

For example this view with only pages, we could free up and clean up the look a bit with hiding the now unnecessary middle navigation / source list.

Something like this:

[thupsi]

This has been requested in #18327 and #17779 (comment) 🙂