Bug 158778 [Viewers] request for remove(parent, index) API on tree viewer
3.3 It would be helpful to have a 'remove(Object parent, int index)' method on the tree viewer to complement that 'replace(...)' and 'setChildCount(...)' APIs. The debug platform requires such a method to implement filtering in virtual tree views. Rather than performing a 'replace/remove' based on elements, the content provider can make one atomic call to remove an element at a specific index.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
createTreeItem(widget, element, index);
			}
		}
	}
	/**
	 * See if element is the data of one of the elements in items.
	 * 
	 * @param items
	 * @param element
	 * @return <code>true</code> if the element matches.
	 */
	private boolean itemExists(Item[] items, Object element) {
		if (usingElementMap()) {
			Widget[] existingItems = findItems(element);
			
			if (existingItems.length == 0) {
				return false;
			} else if (existingItems.length == 1) {
				if (items.length > 0 && existingItems[0] instanceof Item) {
					Item existingItem = (Item) existingItems[0];
					return getParentItem(existingItem) == getParentItem(items[0]);
				}
			}
		}
		for (int i = 0; i < items.length; i++) {
			if (items[i].getData().equals(element)) {
				return true;
			}
		}
		return false;