Navigation panel :: user defined zoom :: shortcut ?

[thomaso 74]

Is there a way to define a keyboard shortcut for a user defined zoom-% in Navigation panel?

Or alternatively, to alter the 100-%-zoom of the default view menu zoom shortcut "cmd-1" from 100% to 85%?

[ I use a second monitor for the main document window at a macbook; both screens have different pixel-sizes. On the macbook Affinities' 100% zoom is perfect - but on the external screen it would be 85%. ]