MS XML Notepad 2007<BR><BR>edit: just to clarify, this is an xml file editor that has a tree view pane on the left. You can right click and expand the whole tree, or leave it collapsed. More options ...

To make a tree diagram in Excel you will need to utilize third-party diagramming tools, such as Lucidchart that allows you to create a tree diagram in Excel. These are known as add-ins to the program.