If there was a web app called "Question and Answer" then the tag would be a good fit and need to be created for questions about it.
But since the example here is a tag based on a broad topic matter instead of a specific web app or website, it would not make a useful tag to have or create.
These tags would be fine as an addition to the ones already there, but not as a total replacement to the general trello tag that already exists.
Going through and removing that and replacing it with a subset version of the parent is a net loss. It's creating a tagsonomy division that only splits the focus.
The web app is Trello, so it makes sense to have ...