I typed three semicolons into Excel and found its strangest formatting trick

A custom number format has four slots
Leave every one of them empty, and Excel draws nothing
Formulas still read the hidden value
Blanking the display never touches the data underneath
This beats hiding columns or turning the font white
Both of the obvious workarounds fail in ways this one does not
It hides the number, but it does not hide much else
Where three semicolons stop being enough
Where I would take this next
The display layer is worth using on purpose