title: Custom editor in MPS
body: <p>I have an concept in Jetbrains MPS which I would like to create a custom editor for.</p>
  
  <p>The concept have a number of children.</p>
  
  <p>For each child I would like to display the child's own editor but with a "-" in front of it.</p>
  
  <p>I'm not completely sure I'm trying to solve this in the right way.</p>
  
  <p>But my first attempt is a custom cell looping over the child nodes. </p>
  
  <p>My problem is that I can't figure out how to find the editor cell of the child nodes:</p>
  
  <p>My cell provider: </p>
  
  <pre><code>return new AbstractCellProvider(node) {
  @Override
  public EditorCell createEditorCell(EditorContext ctx) {
    EditorCell_Collection cells = EditorCell_Collection.createVertical(ctx, node);
    foreach n in node.elements {  
      EditorCell_Collection a = EditorCell_Collection.createHorizontal(ctx, node);
      EditorCell_Label label = new EditorCell_Constant(ctx, node, "-");
      a.addEditorCell(label);
      cells.addEditorCell(a);
  
         how to add the child node's editor here? 
  
     }
  return cells;
  }
  </code></pre>