obs:
1 - value 2.10 and a family parameter can be varied
2 - the values 5.596…, 11.707…, and 18.010… and the distance between families that has a length of 2.10 or varied

I’m trying to get the list in blue in the attached figure, I made a sketch with this rectangle showing what I want to get in the indexes below the new list

Based on what you are showing in blue, you are only taking 0 from the top list and all numbers from the middle list and then adding 2.10 to all of those numbers except for the last number in the middle list. Assuming 18.010 is the last number in the middle list. It’s highlighted so we can’t see it.

Understand, this is how we are seeing it. So you can see why we are asking you to be more specific of what you want your end result to be.

Look at the Genius Loci node List.SortNatural if you are wanting to sort the numbers.