Left-Right Scrolling Issues

First, the positioning of this left-right bar is uncomfortable and clunky, hard to find with my mouse, and unresponsive (sometimes my click will get “lost” despite holding down mouse 1 and dragging, and it’s very frustrating to repeatedly do)

I’d be able to ignore this issue but my second problem is: I use a mouse with a side scroll wheel and this scrolling is never picked up.