Can i delete all posts by a member on a facebook group all at once
If I remember they introduced this feature or planning to introduce soon.
Removed member clean-up: to help keep their communities safe from bad actors, group admins can now remove a person and the content they’ve created within the group, including posts, comments and other people added to the group, in one step.
I don’t know if it’s activated now and also don’t know if it’s possible to remove a member’s all post without removing them from the group.