Hello,
The problem is that TabView already uses a scrollView (you can find it on the "Pages" GameObject), and it seems you can't have one scrollView on top of the other and have the two work together :/
What you can maybe do, is take a look at the "TabPagesScrollDetector" script, and see here, that we are doing some custom dragging to move between the tabs... you could have your own custom dragging two, you'll receive the two callbacks "OnDrag" and "OnEndDrag" and do whatever you want with that to move your own list...