Hi @가영 김 ,
I'm afraid you cannot continue to use Manifest V2 before Edge stops running Manifest V2 extensions, even if it is not registered in the store and manually installed in Edge. That is to say Edge will not recognize Manifest V2 from whatever sources. However, you can still use Manifest V2 for now since the migration is postponed, and please pay attention to the timeline update.
For more information, please check the timeline in this doc.
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Best Regards,
Shijie Li