Piebald allows you to merge one tag into another. Hover the tag and click the merge button:Then choose a tag to merge into, and click Merge:Clicking Merge on the fish tag would merge it into the shell tag; at the end, there would only be the bash and shell tags.
If you have some tags that make sense in only certain projects but that don’t make sense globally, you can create a tag on that specific project. Hover the project, click the settings icon, and select Settings.