In brief
outline-offset sets the distance between an outline and the element's edge. A positive value can separate a focus indicator from a strongly coloured border.
Useful to know
outline-offset sets the distance between an outline and the element's edge. A positive value can separate a focus indicator from a strongly coloured border. [1]
It is not an outer margin that rearranges neighbouring controls. With a larger offset, check tight panels and edges so that part of the indication does not disappear.
Sources
For further detail and to check the information: