How do I make WinEdt show the TOC (Table of Contents) used for navigation? Similar to the TOC visible in the image below (source: WinEdt Snapshots):
Click in menu "View" the entry "tree". This will open the tree panel. To update it click in the panel on the left icon (build tree). This will build the tree of the main file (if there is a main file) or of the current active document.
To set a main file click on the small document with the + on the left of the second icon row. To remove the "main file status" click on the small document with the -. You can see the name of the current main file (if there is one) on the right in the status line at the bottom.