Should there be a tag for VSO. My organization exclusively uses the Microsoft stack and so I have questions I would like to tag with VSO to indicate that I'm using Visual Studio Online, as opposed to the on premise TFS/VSTS for my build/release/test agents
Tags are created when added to a question, you need 150 reputation to create tags.
In those cases where you don't have enough reputation to create them, drop a line at end of your question on main site so someone can add it to your question.
I've added the vso to one of your question, you can now go and complete its wiki and excerpt.