Sorry, I didn’t notice this earlier.
The most basic tags would be the class/mastery tags found in the table @ Build Compendiums. Just include the tags for Witch Hunter, Occultist, and Nightblade to start.
There should be a place for “optional tags” and that’s where you’d put them.
Even if you don’t intend to apply to the build compendium, having even just Witch Hunter tagged would make it easier for people to find your build later.
Edit: Quote from eisprinzessin “Minister of Information” in the Build Compendium:
“As thread owner you can add up to five tags to your initial post. In addition to the class you can specify damage types, play-style and other descriptors. Forum regulars can create new tags, but activity before the forum overhaul in June 2019 will not be taken into account. PM me, if you miss a tag and cannot create it yourself.”