Hi dave_3d
It seems that it lacks of translation in language file.
Kindly check these files:
/administrator/language/en-GB/en-GB.plg_system_t4.ini
/administrator/language/en-GB/en-GB.plg_system_t4.sys.ini
and make sure that you have this translation:
T4_FRONTEND_EDIT_GROUP_LABEL = "Template Front-end editor"
T4_FRONTEND_EDIT_LABEL = "T4 edit layout"
T4_CONFIG_FRONT_EDIT_FULL_LAYOUT = "Full Positions Layout"
T4_CONFIG_FRONT_EDIT_CLEAN_LAYOUT = "Clean Layout"