So while you can't (to my knoweldge) do this in a single sheet, but you can do it in a dashboard with 2 sheets. I have a State/Category sheet and a Category/City Sheet.
I place them in a container on a dashboard and set up 2 actions.
The first filters the City sheet to the state/category selection, and then collapsed the city/category sheet when nothing is selected
This one is optional...but the following action part-collapsed the State sheet to just the selection. This is nice as it gives more screen space to the city sheet.
Hope that gives you the interactivity you need, and makes sense
Drilldown on click_SR.twbx 1.2 MB
This will do! Thanks a lot Simon!!