In my function as a Developer for WMDE (@Michael ), I already have a GitLab account: https://gitlab.wikimedia.org/migr
However, I am also a regular volunteer and would like to manage my more complex user scripts with git and GitLab.
Should I do this with my existing account (like I use my GitHub account both for my private and work projects), or should I request a separate GitLab account (like I have a separate Phabricator and on-wiki account)?
There is currently no community or Wikimedia Foundation requirement for separating paid and volunteer contributions to Wikimedia's technical projects. All technical contributors are equally bound by the https://www.mediawiki.org/wiki/Code_of_Conduct and the license terms of the codebases they contribute to.
If you have concerns about additional rules that may be imposed by your employer you should consult your employment contract, employee handbook, or other employer specific policies.