Sorry, I think I might have confused the discussion by talking about major/minor tags – that was mostly a lead in to the actual suggested feature: differentiating active/non-active tags in the tag list. Where my definition of an active tag is one that applies to any draft in the inbox.
As in my recent question about automating a reset of daily tasks, let me explain what prompted me to think about this today and maybe my intention will be clearer.
I have a tag for drafts relating to an ongoing project. Today I finished this project and archived all these drafts. Since the project is done, I don’t want the tag to stick around forever in the tag list. This is exacerbated by the tag name starting with A, so it’s also at the very top of the list 
I have used the “Only Tags in Current Filter” setting which is very handy, but I don’t think it’s exactly the same as what I’m talking about. If this setting caused the tag list to filter depending on the visible tab (inbox/archive/trash) – even without any tag selected – then I think this would indeed cover my request.