No there isn't a bulk operation. You could have uploaded the videos to the group or Chanel from the start to associate them.
Stream (Classic) isn't getting any more improvements as we will announce a retirement date for it as soon as the migration tool is ready (hopefully later this year).
You should use Stream (on SharePoint) which is putting your videos directly into SharePoint, Teams, and Yammer. There are much more grouping, organizing, bulk options capabilities because your videos are files like any other.
See what's you can do today with videos in SharePoint: https://aka.ms/streamroadmap