Currently, the Shift + click action (when SelectionMode is Extended) selects only the expanded items. Any child items that are in the collapsed items collection of a node won't get selected.

Add a mechanism to allow this type of selection. It can be built-in or some events or method overrides can be introduceds in order to be bale to easily interfere and customize the extended selection.

When dragging and dropping an item, to get the current item's place in the collection you would need to either use the underlying collection bound to the ItemsSource property or get it via reflection. Instead, change the ParentView and RootView properties of the HierarchicalChildCollectionView, to public, to not use the reflection approach. 

We have many use cases where we have multiple panels and we want a tree control (TreeListView or TreeView) to control the contents of the other panels based on selection. Because the selection always happens on MouseDown instead of MouseUp it is impossible to drag & drop items from the tree without changing the selection and thus the contents of the other panels.

The control does not have a build-in expand/collapse animation. 

Expose API to allow customizing the appearance of the tree lines.

Add a mechanism that allows you to sort each child level separately. For example, by applying a different sort descriptor to each child hierarchical view collection.

 

Research a possible way to improve the expanding performance of TreeListViewRow.

Asynchronous mode for ExpandAllHierarchyItems()

Currently, the RadTreeListView control does not fully support the merged cells functionality due to the different levels of the hierarchy of the items displayed by the control. 

Currently, setting HierarchyIndent property does not work as expected for nested rows.

The goal is to expand a second node each time you expand a particular node from the RadTreeListView. The data of the second node is loaded on demand, but it is not shown when the node itself is expanded.