For the graph view, an implementation of tags as nodes with a different connecting linetype (dot dash or something) would add another layer of information to the graph that reveals the relationships among cards with tags. This would be especially helpful for those that do a fair amount of organization with tags. An on/off toggle would also be helpful, for those that may not want to see tag nodes and their connections in graph view.
Simply filtering tag(s) within the graph view’s current implementation does not offer this layer of information.