Hello,
This suggestion is related to this one but also kinda different.
I noticed the color picker tool, when configured as "Average (*x*)", will only return the average color when the cursor is inside the document/canvas. When outside, it will return the color of the pixel the mouse pointer is above, and not the actual average color of the zone.
It would be nice if the tool could return the average color of the zone, no matter its location (inside/outside the document/canvas, inside/outside the program, whatever the monitor # the cursor is in, etc.).
For example, when selecting the color picker tool in average mode and pointing to a 2nd monitor / another window / outside Affinity Designer/Photo, it should return the actual color average.