Multi-format in WER
AFAIK, that's not possible. (Especially since mutli-format required a special sanctioning, which was done only for Nationals (and maybe some very special tournaments) back then.)
You can get around the issue by either running two separate tournaments (probably the better option) or run the ‘multi-format event’ in Swiss mode only, manually creating the pairings for the draft portion. (Which would have the drawback, that the whole tournament would be rated as either Limited or Constructed - if there would be different ratings ever again…)