I was going to ask the question is there a limit to the number of items that can be shown on an Excel SUBNM list. However, I just figured, why don't I try instead of ask.
I pointed SUBNM against the longest dimension I have, in this case it's }LineNumber.

First good news is that it displays all 10,000 items. The second good news is I don't believe my longest dimension will get to 10,000 items. (Famous last words?)
Only question I now have left, any performance hits in Excel anyone's seen with pointing SUBNM against such a long dimension? I'm using PA for Excel.