I have been using BitBucket for a while, now I have a lot of repositories in there and was trying to find a way to organize them. Through search, I found out about gitLab and apparently it allows us to tag projects and I’m assuming filter through them. The tagging part seems easy
I have just started running GitLab community recently. So far I have only used labels for issues, but it is my understanding they cannot be used ‘globally’. I cannot answer for sure if they should be available for your use case, if not you may want to chime in on that related ticket. There is a labels API that they have been iterating on, and there is some documentation for it. Sorry I can’t answer directly your question, but hopefully this helps point you in the right direction.
At the moment, I gave all the repositories labels. Then made an issue using that label. The issue just describes the project. I assign the issue to myself and as a result I get a global index (log) of my repositories. Not ideal but good enough