One figured-bass line serves all upper parts realizing over it — figures aren't duplicated per upper voice

In continuo texture (one bass line, several upper voices realizing the harmony), the figures are authored and rendered exactly once, under the single bass staff — never repeated under each upper voice's staff.

Read (figures belong to the bass line); standard basso continuo engraving practice, universal across historical and modern editions.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.