Word 2010 -- How can you make heading 4, 5, etc.. visible in the table of contents?

You can use the same method as in Word 2007.

1. Click the 3 vertical dots in the box that say "Update Table" at the top so the whole table is selected
2. Right click and select "Toggle Field Codes" (or type Shift+F9)

You should see {TOC \o "1-3" \h\z\u}.

3. Edit the part where it says "1-3" to whatever amount of indents you'd like e.g. "1-4" for 4 indents

4. repeat Steps 1 and 2

5. Click "Update Table...".

A simpler solution would be to select the table of contents and click Alt+F9. You should probably see the following code: { TOC \o "1-3" \h }

Change 3 to 4 and the problem should be solved.

Again click Alt+F9 to see table of content.