unpivot data and handle merged cells without using Power Query (Unpivot_Toolkit)

Thanks, Peter! Really appreciate the kind words and the thoughtful breakdown.

I'll be honest. Your three points are a little open-ended, so I may not be reading them exactly as intended! But if I'm on the right track, here's how they map to some design decisions I made along the way:

On option 1. it's definitely the most intuitive approach, and honestly the most Excel-native one. The catch I ran into is performance. Once fill-down/fill-right logic is a part of the formula chain, recalculation overhead grows noticeably compared to working against a plain range reference. I benchmarked this across a few scenarios using a custom LAMBDA benchmark tool, and the difference was significant (x2 slower).

I even update the function to use INDEX instead of CHOOSEROWS/COLS to return references not arrays and got 2 sec boost in worst case scenarios. I'm not entirely sure why, but the numbers don't lie.

On options 2 & 3. if you're pointing toward aggregation and re-pivoting as natural next steps after unpivoting, then totally agree. I am happy to make a separate version of PIVOT/GROUPBY that integrates perfectly with UNPIVOT_PLUS without DROP/TAKE Headache soon. UNPIVOT_PLUS is already sitting at 9 parameters (PIVOTBY is at 11), which I feel is the upper limit before users start bouncing off it (though I know that's no issue for power users).

Integrating both into one will be a whopping 20-parameter machine!

If I've misread any of this, feel free to correct me. Always happy to dig deeper! And yes, choice is indeed good.