SONAR-12758 allowed a project extension to consume the current branch|pr. The new property passed to the extension has been documented.
However, it is pretty useless for classic extension (which appears in the "More" menu of a project) because the "More" menu is only displayed for the main branch.
It seems that the menu was intentionally hidden for non-main branch because the branch|pr property wasn't passed to the extension. Now that it is, we should make the menu available no matter what the current branch|pr is.