The section to control whether beta features of this extension may be used or not is no longer shown on "Special:Preferences#mw-prefsection-editing". The section for alpha features is still there.
The section header used to be "prefs-beta" until MW 1.19 or MW 1.20 changed to "prefs-editor" in MW 1.20 or MW 1.21 though (message unfortunately not included in core thus rendering <prefs-editor>.
Version: REL1_22-branch
Severity: normal