For users on Flutter 2.8.0 or greater (or Dart 2.15.0 or greater),
DevTools should now be launched via the dart devtools command
instead of running pub global activate devtools.
DevTools 2.8.0 will be the last version of DevTools shipped on pub,
and all future versions of DevTools will be shipped as part of the Dart SDK.
If you see this warning,
be sure to open DevTools via dart devtools instead of from pub:

Performance Updates

Added a new “Enhance Tracing” feature to help users diagnose UI jank
stemming from expensive Build, Layout, and Paint operations.

The expected workflow is as such:

User is investigating UI jank in the performance page

User notices a long Build, Layout, and/or Paint event

User turns on the respective tracking toggle in the “Enhance Tracing” feature