@forbzie22_0253,
From an API standpoint, I believe only npm packages support server-side tags. Rubygems might, but in any case we strongly advise against using them: https://blog.inedo.com/npm/smarter-npm-versioning-with-semver/
Server-side tagging is not likely something we will support in the future. Deprecation and Listing are really only there because many of the client APIs support them.
I'd need to see a strong, specific use case. If it's related to quality (e.g. dev, staging, prod), then it's a "hard no" because our solution to quality is prerelease version numbering/tagging with repackaging.
I do know that Sonatype Nexus has always supported tagging, but their repository is more of a "fileserver with server-side metadata" and ProGet is package-based. The only documented use case they have for tags has been quality, and our solution/approach is far superior.
Cheers,
Alex