Yeah, it's more about accenting certain notes, so dragging/painting a curve doesn't work. And I know the notes have velocity handles, but they're tiny and a miniscule bump will affect the velocity too much. I assume there has to be some way, even if it's a custom action, but I just wouldn't know where to start.
View>Filter events : you can filter for certain values on the piano roll to see hihats only you can then shift+click to select the notes you want to accent, or use the Position in measure setting on the filter window and then Set selection option View>Event properties : type +/-10 in the Velocity field (set a relative value instead of a specific value)