Dear Hidehiro,
Apologies for the very late reply. There was an issue with the portal that had prevented us from receiving notifications of new posts.
Your understanding is correct that, in OSCAR/Surface, for a station that is sending METAR and SYNOP, only the reporting cycle of SYNOP has to be declared in OSCAR/Surface. Currently, METARs are not monitored via the WDQMS Web Tool.
And yes, if you wish to describe the reporting cycle for METAR, you should create a separate reporting schedule.
Thank you, best regards,
Luis