Why can't I change the slider values when using the mouse scroll wheel?
Capture One 20 introduced scrollable Tool Tabs and altered the default behavior of the mouse scroll wheel. That way, using a scroll wheel over a slider will no longer change the value as it did in the previous versions of Capture One. Instead, the tools in the scrollable part of the Tool Tab will be scrolled.
To revert the behavior to the one as in the previous Capture One versions, open the Preferences window. Go to Capture One -> Preferences on Mac or Edit -> Preferences on Windows. Then go to General ->Tool Tabs and enable Scroll wheel changes slider value.
The default behavior of the mouse scroll wheel now will be changing the values when pointing a cursor on a slider and scrolling. While the Alt button + Scroll wheel will scroll the Tool Tab.