The purpose of the Content Library is to share pre-approved content to your team members in Groups. Therefore, we currently do not give team members the ability to edit the content before they send it.
If there is a desire to make changes or customize a piece of content in the library, the team member should copy the text of the post, go to create a new message of their own and paste the text, then make their changes. If the team member is a Guest role, this will require their post to be sent to their Admin(s) for review. If the team member is a User role, their post will go to their Admin(s) for review only if it triggers any keyword filtration setup in Gremlin Social.