Javascript for municipalities in drill-down questions

Hello, QXM Community
 
For my research - I have to prepare a drill-down question referring to a. “regions” b. “provinces in the region,” c. “municipalities in each province,” d. “school’s id for each municipality” in the Italian context.
 
Unfortunately, the .csv I’m using exceeds the 30row limit, and there’s no way to overcome this problem (even splitting the file into other CSVs) without Javascript. So far, I have understood how to use Javascript in Qualtrics, but I would like some help making the question work.
 
In particular, as far as I can understand in some previous comments, I read that I should store my data in a local JS array of objects or use ajax to get it from an external source. Nonetheless, I would like to know precisely the steps that I should take regarding:
-            The storage of the data
-            The script to populate the drill down in Qualtrics and to make it work (so that if someone selects a region, they can select their city among that region’s cities and so on).
Maybe someone has a similar script that I could adapt to my context.
 
Unfortunately, in the Community, I just found some advice about JS in general but not applied to Qualtrics with the drill-down target.
 
Thank you all in advance
g