In Numbers, this window pops up, I think, if the spreadsheet has been edited in Excel.
Warnings -
This spreadsheet may look different. Here's a list of what changed when you opened it in Numbers.
How do I close that window if it pops up? I tried an if condition and chose
"window condition", "title contains 'Warnings' "
But KM displays False.
That pop-up is a non-standard window, and thus doesn't make itself visible to KM in a way that lets it verify its title with the usual window conditions. Try this macro that uses GUI scripting, which as far as I can tell is the only way to close this window without resorting to Found Image: