What you're looking for is the timing setup panel. When you go there, you can create new timing points (make sure to check off the inherit previous point's timings option), which you can either add manually or copy the current position of the song. Then, you can edit the SVs by changing the multiplier in the slider velocity section, with higher numbers making it scroll faster, and vice versa. It'll take a while to get used to and you may have to spend multiple hours just adding timing points and testing them, since it can be really tedious and mathematical.
Here's a very helpful in-depth guide to using SVs in case you're looking for a longer read on the topic:
community/forums/topics/155780?n=1(There's also another even longer and more in depth guide out there that I remember reading at one point but lost, so if I find it again, I'll make sure to update this reply!)