Let us put cell contents in a header or footer
Lotus 123 used to have this and it was very handy. You'd nominate a reference to a cell, and the contents of that cell would appear in the footer. It was useful when producing a multi-page report, so the report serial number would appear on every page.
I've got a macro doing this at the moment, but I want to phase out macros because they're fundamentally insecure.