The PR #6011 has no link with externalsensortemp, that’s for unoccupiedheatsetpoint and Occupancy specific attrubutes (that I recently updated to reuse an existing config attribute instead of creating a new one for Local_Occupancy because that seems ed to cause some discussion about the proposed name).
config/externalsensortemp is already existing in code https://github.com/dresden-elektronik/deconz-rest-plugin/blob/master/devices/generic/items/config_externalsensortemp_item.json and that’s the one I used without patch. Just updating the DDF file to match the specific Stelpro or Sinopé attributes in thermostat.