Seeing it in a context without a UI to show you the row and column numbers felt a bit awkward to me too...

... and it made me wonder if some other syntax would work better, which made me think that maybe something like this would work?

    =sum(column | 2+ | above)
         targets whole column "stream"
                  second item and later
                       above this cell
         pipes manipulate the target "stream"

I'm waffling between rx-like and unix-like for terms though. Or something else. But a much more relative-and-whole-sheet-focused language seems like it could be a lot nicer than pinning cell IDs everywhere.

Note that you can represent much more complex spreadsheets using Sheet Markup, and while in the above example it might be clear what SUM(COST) would mean, in a more complex spreadsheet, with multiple different tables, it might be ambiguous.

As for why one would possibly ever want to use Sheet Markup for mode complex spreadsheets, one use is as a way to interact with an LLM. We've started to see some interesting results using GPT-4 to analyze various kinds of spreadsheets that have been encoded in Sheet Markup.