As of October 2024, this still works, but will only detect the admin in "Preview Mode" when previewing new themes or theme changes from the editor. If the admin is browsing the site normally, the preview bar is not output, and the `adminBar` we used ...

Just responding to say, us too! Very excited by the possibility of this feature, but there is no documentation on how to actually utilise it.The new 'Dawn' theme doesn't seem to use these features, so doesn't' act as a good reference.I find it so odd...