GitLab is used only for code review, issue tracking and project management. Canonical locations for source code are still https://gitweb.torproject.org/ https://git.torproject.org/ and git-rw.torproject.org.
There are some doxygen warnings about unclosed or unbalanced groups.
To enable design management, you'll need to meet the requirements. If you need help, reach out to our support team for assistance.