No way to author an accidental attached above/below an ornament symbol (trill, turn, mordent)

An accidental modifying an ornament's auxiliary pitch (e.g. a trill needing a flattened upper auxiliary, or a turn with a chromatically altered upper/lower note) is placed above or below the ornament symbol itself, not as a normal note-attached accidental.

Gould, 'Ornaments' chapter, explicit diagrams of accidentals above/below trill and turn symbols; Read ch.9, same convention; SMuFL defines dedicated combining accidental-above/below-ornament glyph positions.

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