Well, I wrote a nice guide on searching, that can be leveraged here.
Using your example, for Uncategorized and ‘Zwift’ as the one term, you get plenty of results:
https://www.trainerroad.com/forum/search?q=%23uncategorized%20zwift
More words can be added, including the other advanced options and ‘Sort by’ to filter results more.
As to tags, I am fine with adding a Zwift one in particular, but I don’t know it adds much over using it in the search term. I have no control over that, and will leave that consideration to @IvyAudrain to review.