We can add the data via the "Add Data" widget to the map, but I'd like to go further and display some statistics about the added data. To do this for the "default" data I use the Text widget which is connected to the data (it allows me to display whatever I want). But it seems that Experience Builder cannot "see" the data added with the "Add Data" widget. How can I connect the added data to any other widget?
In this image EB propose to connect Text widget to the "default" data on the map.
This is not an option as Experience Builder has no way of knowing what data your end-user may add. Getting text to react to data added at runtime would take developing a custom widget and even then you would likely need to know what kind of data the end-user is adding and how it is structured.