Hello,

I tried this recently, but It I was not satisfied with the result - I was not able to hide scrollbar properly.
However thanks to recent updates, you can now try it yourself.
Go to Options page, and to the field "Custom CSS styles:" enter this:

.dials > a > div {
overflow-y: scroll;
margin-right: -29px;
}

That will enable scrolling of the dials, plus hides the scrollbar.
Alternatively, if you want to see scrollbar and only when it's really needed (when the image is long enough), you can use this:

.dials > a > div {
overflow-y: auto;
}

I hope this helps :)

Best regards,
Juraj Mäsiar