A family of Microsoft word processing software products for creating web, email, and print documents.
I don't see much difference between the Developer tab in Word 2007 and the Developer tab in Word 2010. The methods of choosing to display it are different, however. In Word 2007, there is a check box at Office Button | Word Options | Popular to "Show the Developer tab in the Ribbon." In Word 2010, you have to go to File | Options | Customize Ribbon and check the box for the Developer tab in the list of displayed tabs.
But I also don't see anything on either Developer tab that has anything to do with toggling the display of field codes. As Doug says, you can do that with Alt+F9. If you are referring to protecting and unprotecting legacy form fields, then the most efficient way to do that is to add the Lock button (in the Commands Not in the Ribbon category) to the Quick Access Toolbar.