I've been able to "freeze panes" for horizontal rows, so the column headings
stay in place as I scroll down. But when I also try to "freeze panes" for
vertical columns, so the row headings will stay in place, after I select the
column to freeze, the only choice I have is "unfreeze panes".

Is this because you can't do both horizontal and vertical freezes on the
same spreadsheet. Or is there a different way to accomplish this?