Messa di voce hairpins are single gradual dynamic items that appear as a pair of hairpins without an immediate dynamic in the middle. They indicate that within their duration, the volume either increases then decreases, or decreases then increases.
In Write mode, messa di voce hairpins have three handles: one at the start, one at the end, and one in the center. This is different to separate, ungrouped hairpins, which each have a handle at the start and end.
You can move the graphical peak of messa di voce hairpins by moving their center. In Engrave mode, you can use messa di voce center handles to control their center aperture.