Martin,
OK, here is the change. In the apps jimu/MapManager.js find the _show2DWebMap function and make this change below (line 9):
....
var mapDeferred = this._createWebMapRaw(webMapPortalUrl, webMapItemId, this.mapDivId, webMapOptions);
mapDeferred.then(lang.hitch(this, function(response) {
var map = response.map;
map.hideZoomSlider();
map.disableKeyboardNavigation();
....