Tagging is limited to the tags that have been approved by moderators. You can see all of the current tags at the bottom of
this page.
Some sites/forums allow user-assigned tagging, so it becomes something of a popularity/trending hashtag. The forum approach has been to use tags in a more structured way, to create sub-forums. For example, all of the
sub-forums under Equipment are created by tagging. (Not to complicate things, but there are some sub-forums such as the different routes within Spain or France, that are actual buckets where the threads reside.)
From time to time, we create new tags and tag-forums, but we have tried to keep the number under control. After all, there are hundreds of possible tags, and most threads could easily get a dozen.
There are other ways to organize and find threads. For example, if you do a search in title-only for "poem" you will find
these threads.
@malingerer has a thread titled "Poems for seekers" with 760 posts since 2015. I think that is a better idea than tagging 760 threads, each with a different poem. Perhaps
@William Garza can create a single thread to which he can add new poems rather than starting new threads.
We will separately consider the tag collection and whether there is a tag that could collect poetry as well as other topics.