Formatting the auto-numbering

Hello there !

I’d like my auto-numbering (using the <$n> placeholder for example) to start at 001 instead of 1. I’ve looked into the manual and the Placeholders help menu, but I didn’t find anything about that.
Would it be possible to add some fine tuning options for the numbering placeholders ?
like <$n3> for a 3 digits numbering for example ?

Thanks !