Merging Identities: Managing QA Events in Mixpanel After Login

Hi all, question about merging identities. We're using Segment as a source. We are going to filter "QA events" (they have a flag) from reaching Mixpanel altogether through a filter on Segment's side. However, before login this flag will always show false (since we don't know the identity of the user). Post-login we have that information. Is there a way to delete these events after they reached Mixpanel?