This is hilarious because the official documentation[0] suggests that you use hidden divs to store data as json if you need to share it between callbacks (which is more common than they would have you believe). And good luck serializing data structures with complex types in them.
Python frameworks are all fun and dandy untill you look under the hood or try to push the envelope.
Personally for all my dashboard needs I have found R's Shiny to be the best.