I can't scroll down/up by clicking on the scroll bar to the right in Quest Lines. I have the same issue when editing quest lines but scrolling by clicking works perfectly when I'm in the quest designer.

I've tried using

Better Questing-1.3.161
RFExpansion-1.3.19
Standard Expansion-1.3.98
on forge 2095

And then i decided to try older versions to see if it was a new bug. Turns out that i wasn't able to scroll on any of the 1.10.2 versions on curse (between 1.3.161 - 1.3.140) and while testing i only used Better Questing so I'd know if it was a compatibility error, forge version used was 2098.

I guess this issue is only relevant for people who don't have a scrolling wheel.

The issue is fixed in the 2.3 versions so I'm sure the mod author is aware of it and will fix it in the 1.3 versions soon enough.