Views Geolocation field proximity: How to alter views field setting
Digging through the exported views.yml config helped me to get on the right track:

function MYMODULE_views_pre_view($view, $display_id, &amp;$args) {

  if ($view-&gt;id() == 'WHATEVER' and $display_id == 'MY_DISPLAY') {
    $allFields = $view-&gt;display_handler-&gt;getOption('fields');

    $user = _MY_BUSINESS_LOGIC();
    if (!$user-&gt;get('field_geo')-&gt;isEmpty()) {
      $allFields ['field_geo_proximity']['proximity_lat'] = $user-&gt;get('field_geo')-&gt;lat;
      $allFields ['field_geo_proximity']['proximity_lng'] = $user-&gt;get('field_geo')-&gt;lng;
      $view-&gt;display_handler-&gt;overrideOption('fields', $allFields);
    }
  }
}