message: Disable expand/collapse panel at design-time
diff: @@ -782,6 +782,7 @@ export class PanelModel extends PanelModelBase implements IElement {
  * @see isCollapsed
  */
  public get isExpanded() {
  + if (this.isDesignMode) return;
  return this.state == "expanded";
  }
  /**
  @@ -789,6 +790,7 @@ export class PanelModel extends PanelModelBase implements IElement {
  * @see state
  */
  public collapse() {
  + if (this.isDesignMode) return;
  this.state = "collapsed";
  }
  /**
  