Use case or problem
Right now, there is an option to show or hide tags on the graph, so you can either see all of them or none. I’d find it useful to be able to choose which tags to see on the graph.
When you switch tags on, the tags could turn into a collapsible area. Within the area, there could be a ‘New tag’ button, similar to the ‘New group’ button in the Groups area.
When you add a tag, that tag would be the only one shown on the graph. When you add another tag, both would be shown. And so on.
Each selected tag in the Tags area would have an X next to it, just like color groups. There could also be an option to disable all selected tags (as a toggle), thus showing all tags.