fix: auto-place elements vertically in sub processes

lib/features/modeling/util/ModelingUtil.js

@@ -46,17 +46,19 @@ export function getParent(element, anyType) {
  *
  * @return {boolean} false for vertical pools, lanes and their children. true otherwise
  */
-export function isDirectionHorizontal(element, elementRegistry) {
+export function isDirectionHorizontal(element, elementRegistry = undefined) {
 
   var parent = getParent(element, 'bpmn:Process');
   if (parent) {
     return true;
   }
 
-  parent = getParent(element, 'bpmn:Participant');
+  var types = [ 'bpmn:Participant', 'bpmn:Lane' ];
+
+  parent = getParent(element, types);
   if (parent) {
     return isHorizontal(parent);
-  } else if (is(element, 'bpmn:Participant')) {
+  } else if (is(element, types)) {
     return isHorizontal(element);
   }
 
@@ -67,6 +69,10 @@ export function isDirectionHorizontal(element, elementRegistry) {
     }
   }
 
+  if (elementRegistry === undefined) {
+    return true;
+  }
+
   // The direction may be specified in another diagram. We ignore that there
   // could be multiple diagrams with contradicting properties based on the
   // assumption that such BPMN files are unusual.