Following is answers from Mendix team, sharing it with those who are interested in this topic
There is unfortunately no other way possible to identify which widget triggers the common Nanoflow. However, to help you more with this query, the simple way to do it is to create a small nanoflow per widget that would just only trigger an actual useful nanoflow + pass some pre-defined parameter.
We are aware that this might not be the most suited solution to most developers, but we have this on our long-term road-map, however, no promises!