We’re in the process of updating the documentation for Zotero 5.0. Some documentation may be outdated in the meantime. Thanks for your understanding.
The Zotero word processor plugin for Word for Mac 2008 doesn't offer a toolbar, instead adding a “Zotero” entry to the AppleScript menu (the manuscript icon to the right of the Help menu):
Most menu commands are also available through shortcut keys.
Word for Mac 2008 lacks support for Visual Basic for Applications (VBA), making it impossible to create a toolbar. VBA support has been restored in Word for Mac 2011, and the Zotero plugin for Word 2011 includes a toolbar in addition to an AppleScript menu folder.