Seems like a potential hackathon project to me. If it's not, feel free to remove the project tag.

This seems like a recent change... it used to be that only the groups used on the page by the map link/mapframe functions would be listed, but it seems now all categories that are defined are added to the list even when unused, making it very very long ? This might be due to a change in how the group parameter is being handled by the parser function ?

In T332774#8717835, @TheDJ wrote:

This seems like a recent change... it used to be that only the groups used on the page by the map link/mapframe functions would be listed, but it seems now all categories that are defined are added to the list even when unused, making it very very long ? This might be due to a change in how the group parameter is being handled by the parser function ?

Sounds like T332661?

IMHO, even if only the used types of listings were shown in the list, the request would still remain valid, because some articles can use lots of different types, resulting in a long list as well.

Asked if this concern is addressed now that T332661 is done. https://meta.wikimedia.org/w/index.php?title=Talk%3AWMDE_Technical_Wishes%2FGeoinformation%2FNearby_articles&diff=prev&oldid=24848136&diffmode=source