Hi, thanks for posting an interesting project.
As I understood you want to make some user interaction stuff outside chart canvas.
ChartJs provides good documentation which will help us to make some changes on user interaction events for example filtering multiple canvas charts etc...
I'm an experienced web developer working on javascript based charts for over 5+ years and I think I can easily help you out with the project.
The common problems with chartjs is accessing chart instance, we can simply get chart instance via global Chart object and canvas element ID.
So with all of that I think I can easily help you out with the project.
Please send a message and let's discuss further.
Thanks.
George.