I’m trying to group the points based on theier X & Y. I’m using Group by Key values but can do only x or Y. How can we put both conditions together? Group by function maybe??
The intent behind this grouping is, for elements it returns points on top and bottom edges of any element. By grouping this, and giving a condition to filter points with Z of point > Z of other point in the same group, whoch will give two list one for all bottom points and other for all top points.

So basically each X,Y point will have two elevations for an element. I want to group them in that manner, so there will be sublists of indices 0,1 .Later we will group by index with 0 and 1. Basically generating all the top points of an element and all the bottom points of the same elements separately. This way user can choose what points he/she needs.