Most accordion music has been written using AAA notation for the left hand.
A note on or below the center-line of the bass staff is a simple bass note. A note above the centerline represents a chord, which is identified by a chord notation above the staff (M, m, 7, or d).
It would be great if Dorico supported that in some way. One feature that would help a great deal would be expression map conditions based on pitch. This would allow support for standard notation when used with an accordion instrument where the various chords are mapped onto different octaves, like Tarilonte Accordions 2.