Save as revision

Is it possible to save the post as a revision? The current behavior allows to save/update

The issue is this. when editing a post by the user an admin can configure to publish the post or save it as draft/pending. Saving as published will not allow the admin review the post and approve it which is exactly what it suppose to do. Now saving as draft/pending will allow the admin to review the post before publishing it. which again works as expected. The only issue is when saving as draft/pending the original post that was already approved will not be shown to public any more. Is there a way to keep already approved post and only replace it when a revision is approved?