Sooo... I'm working on a 'Sekrit' project (It's the Novel Form of my Terraria Fanfiction. Dang... I suck at secrets... ;P), and a part of that involved using the 'Table of Contents' feature baked into Microsoft Word. As long as you begin your chapters with a title that uses H1, you're fine just letting it loose on your project, and it will auto populate with Titles, Page Numbers (That you can update as you add / remove words from your project), and Hyperlinks to that Chapter. It's wondermous. The 'Problem' arises if you're doing something 'Different' in your Chapter Naming scheme... for example... Using H1 for the 'Chapter X' part, and H2 for the Chapter Name. (I did this so that I could use the Chapter Names Separate from the 'Chapter X' portion in the headers). If this sounds incredibly complicated... That's probably why I ran into problems. ;P
The 'Problem' arose when I wanted to add another chapter to the story. See... you can have the table update the page numbers... or update the entire thing (Redoing all the Formatting, and pulling all the titles anew). I had manually adjusted the formatting of my ToC, and once you do that you can still use the 'Update Page Numbers Only' option... but updating the whole thing means you have to reformat (And in my case, Write in all the Chapter Names again) it. Now... before we continue... you can adjust an incredible amount of formatting option in the advanced Table of Contents generation menus. This problem was because I just went with the default, and then 'Manually' formatted it. If you're just deciding to add a Table of Contents... I'd spend a little bit of time playing around with the formatting options up front, and you can maybe save yourself this headache. >.>
ANYwho... since I needed to update it, AND I wanted to keep my custom formatting, I used this guide, to learn about Field Switches, and re-familiarized myself with Copying and Pasting 'Only' Formatting. (CTRL + SHIFT + C to Copy Only Formatting and CTRL + SHIFT + V to Paste Only Formatting) Specifically... I learned that you can adjust the Field Code to pull multiple heading levels, and then once I did that, I pasted my custom formatting on top of the pulled Table. From there, I merely needed to bring the now separate sections (It by default gives each heading it's own line) together for each chapter... which was as easy as putting in my delimiter of choice (I put a : after that 'Chapter X') and hitting DELETE four times for each line. FAR quicker than retyping everything.
All in all, I love working on this project. I've learned an incredible amount about formatting a novel... so 'One Day' when I end up writing my own original work... I'll be able to adequately format it for private printing. (If I ever go 'Pro' I realize that I'll have to play with LaTeX or something akin to that... Yay? ;P)