There needs to be a way to adjust the volume/velocity (relatively) for all hits on a track.
This could be achieved by modifier + click and drag on any step volume handle on a track. Dragging the handle while holding the modifier would raise or lower all handles simultaneously, while keeping their relative velocity values.
Dragging to the top or the bottom of the volume range would max or zero out the volume/velocity, respectively.
Edit: this could perhaps be achieved simply with the “all steps” button. Perhaps it could toggle between “all steps” and “relative”. When in “relative” mode, dragging the number field would relatively adjust volumes.