Unfortunately DisplayFusion can't control the opacity of the Windows taskbar on the primary monitor. There's a method to replace the Windows taskbar with a DisplayFusion taskbar, but it's not a supported feature, so try it at your own risk. The details are in post #6 here: https://www.displayfusion.com/Discussions/View/anyway-to-make-the-df-pro-taskbar-override-the-windows-taskbar/?ID=3d0cad5b-2ab0-4b2d-acbc-cd2b45389c38#6

Please let me know if you have any other questions at all.

Thanks!