I’m afraid I still don’t follow.
You can use [Convert Mouse Location to World Space] with a normalizer, but that wouldn’t be very practical.
With [Input Mouse Delta], [Get Mouse Position Scaled by DPI], [Get Viewport Scale], [Get Viewport Size] and [Set Actor Relative Location], you can control the actor’s feet. A quick solution would be to also use [Normalize to Range] and [Clamp to Range] to set the sensitivity because 2D mouse coords won’t translate well in 3D space.
If you mean you want to use the mouse to control the actor’s view, you can use [Get Base Aim Rotation] for your camera with [Find Look at Rotation] to change where the actor looks.
As for the widget, I really don’t know what kind of interaction you need,