Buttons

The following buttons are in the tool bar:
Exits Treeview without further ado
Pops up a file browser which allows you to enter a new file or directory into the tree

Displays the Details panel to the right of the Tree panel (default)
Displays the Details panel below the Tree panel
Displays only the Tree panel with no Details panel

Collapses the selected node, so its children are no longer visible
(same as clicking on the handle of an expanded node)
Expands the selected node, so its children are no longer visible
(same as clicking on the handle of a collapsed node)
Recursively collapses the selected node.
Its children, and its childrens' children, and their children... are all closed.
Recursively expands the selected node.
The selected node is expanded, and all its children, and all its childrens' children... This enables you to see the entire contents of a given node. If performed on a node containing a lot of data, e.g. the top of a large directory structure, it may take a long time to complete.

Replaces the selected node with its parent.
You can walk up the hierarchy tree inserting nodes above the current one using this button. It is only available for a node at the top level of the tree.
Copies the selected node to the top level of the tree.
You can assemble a set of nodes of interest at the same level in the tree using this button and the ones listed above and below.
Reloads the selected node.
The selected node is refreshed from its original data, so for instance if a directory node is selected this will cause the directory to be re-read so that any new/deleted files are taken account of. A reload has the effect of (recursively) collapsing the node in question.
Deletes the selected top-level node from the tree.

Adds a new node to the top of the tree containing various types of test data. Investigating this node is a good way to find out about Treeview's capabilities.
Displays Help information in the Details panel.
This has the side-effect of deselecting any selected node.