Here are the current Engine version tags:
The tagging system doesn’t allow for special characters due to the use of tags within URLs. Spaces get replaced with hyphens, periods get replaced removed, and the previous Engine version tags that moved across to the forums from AnswerHub were often just a series of numbers, i.e., 4262 for UE4 26.2 or 43 for UE4 3.0. The best solution was to format Engine version tags as UE4-VERSION to improve this.
The caveat is that expanding this to include hotfixes and updates to that version (4.27.2 as an example) would result in a tag that was UE4-27-2. While this may be preferable to some, the tag list would get bloated and result in less intuitive tagging for many.
As for the issue you are directly facing in tagging, we haven’t been able to reproduce this. Upon attempting to create a Question in that category, UE4-20 appears in the search and is taggable.
