Drop-down menu of "Dashboards" divided into submenus based on topics

We would like to have the attached "Dashboards" drop-down menu divided into a submenu for each topic, maybe with the possibility of choosing which topics to show.

It would be useful in our opinion if it worked like this:
We click on "Dashboards"
it shows the list of topics
we click on the topic we need at that moment
it shows the list of views and dashboards associated to the selected topic

Since we're a service provider we will have thousands of dashboards and views, and having them all in a single list becomes confusing, so we'd like to have the drop-down "folderable"