This question already has an answer here:
Using the Atlas plugin for qGIS how do I set the coverage so that it will only highlight the feature(s) I want but still show the surrounding features as grayed out areas?
This would have been easy if I don't need to work with several thousand features.
I am not asking just how to mask neighboring features. I am asking how to to make Atlas dynamically mask neighboring features of the POI.
The idea is similar to this map here.