GitLab team member here. We have Code Owners [1] and recently introduced Merge Request Reviewers [2]. Our team is working on the author-review handoff [3] as part of their work to improve the overall merge request reviewer experience [4]. I'm sure they would appreciate any detailed feedback you could share on the epics linked below.
1 - https://docs.gitlab.com/ee/user/project/code_owners.html#int...
2 - https://about.gitlab.com/releases/2020/12/22/gitlab-13-7-rel...