I would like to pick a colour from the fill for the stroke
I would like to pick a colour from the fill for the stroke.
So if I choose fill to be the main I would like to change it regardless if I am picking from the fill or the stroke.
You can do it by holding Shift while using the Eyedropper tool
If you mean that you want to make the stroke of an object to have the same color as the fill:
You can click-drag the fill color (in any tool palette with the fill/stroke indicator) to the stroke area right next to it, and vice-versa.
Gordon McAlpin commented
If I'm understanding your request right, you can already do this. Hold shift while using the eyedropper.