Just to see if I understood you correctly, it’s the TILTING feature shown in the video that you’re proposing, right? That’s pretty neat!
I realise you probably know what I’m going to say already but I just want to see if I understood what you mean. You mention not dragging velocities up or down by a fixed amount but to me it seems that it’s exactly what most of that clip is about, adding or subtracting a fixed amount to a set of notes based on their original velocities…am I right? Cause you can already do it in Bitwig and it works in a pretty similar way.
The only difference I can see is that if you push all the velocities to the top and drag them back thay’re going to go back to their original value - which I actually find to be a way better behaviour - to make them all the same velocity you have to bring Velocity Scaling from 100% to 0%.
You can either select different notes with different velocities, open the velocity panel and drag one of the selected notes’ velocity up or down they all move accordingly - exactly like in the video - or you can click on the little arrow next to Velocity in the Note panel and modify the value Mean.
Which also offers the bonus ‘feature’ that, if you need to modify an entire clip you don’t even need to select the notes, you just select the clip and use the Note panel to modify all the notes it contains.