@Paul_Danyliuk
I wholeheartedly commend the solution and creativity.
I suspect the laugh is mostly for the fact that this is required to handle these types of things - the fact that there is a legitimate need indicates it should be something that exists as a top-level function.
I myself used RegexExtract to get outer CurrentValue access so I could do GroupBy(). (I.e.: Map the indices to a: “X1-Y1,…,Xn-Yn” pattern, then used ((\d+)-[^,]+,*(\2-[^,]+,)*), "gm" to group and extract separate lists.)
And… I was absolutely frustrated by the mental exercise required to get the functionality I need as I needed to get things done, not have to reinvent the concept of GroupBy. I don’t want to have to jump through these hoops to do these things, nor have to implement what is essentially a manual-memory-using-multiple-tables turing machine.
And that is not even to mention the fact that you really don’t want to have this in a production document other people will touch.