I was trying to create a unified folder for all my 10 different email addresses to display the messages received today. I couldn't figure out how to create one, so I set the criteria in the Templates Unified Folder and then I renamed that folder to "Today's Inbox". As soon as I hit ok, it disappeared, never to be seen again. So now, I don't have my Templates Unified folder, which I never used, nor do I have the Today's Inbox Unified Folder. So how do I create a Unified folder?

Unified folders are one thing, you are asking about a search folder. ie a search folder of all mail received today.

Press Ctrl+Shift+F and design your search to locate the emails you want. Then save the search as a folder.

I have a search folder setup, but I don't think it works all that well and I've put it in my favorites. I'd actually like to create a Unified Folder. Particularly, I'd like to recreate the Templates Folder and then create other types of Unified folders.