[_dain_]

I wrote another comment that also answers yours for the most part: https://news.ycombinator.com/item?id=32365128

tldr your problem with Excel is that you don't grok tables. They eliminate the need to know the number of rows when writing your formulae.

I don't actually have Excel installed on the machine I'm using to type this, so I can't put my money where my mouth is like the vim guy did[1]. But I'm fairly sure you can achieve your goal with table references and liberal use of the XLOOKUP and FILTER functions. It'll get a little hairy since you have to go from Set -> Inventories -> Inventory Parts -> Parts, so maybe a bit of nesting. But I think doable. The LET function also helps to reduce formula complexity, it lets you make lexically-scoped variables inside your formulae. Use "data validation" to make a dropdown menu for the set names.

[1] https://stackoverflow.com/a/1220118