Function next_pin_ordinal 

fn next_pin_ordinal(indexed: &IndexedDocument<'_>, owner: Scope) -> u32

The auto-name a stamped pin takes ("Port N", tag "N" — Drawing::add_port_auto_named, add_named_pin). Ids count per document, not per block, so the number is read back off the owner’s pins: one past the highest they already carry.