If you are using Chicago Footnote style, jumping back and forth between the References toolbar (to add a footnote) and the EndNote toolbar (to add a citation) is not very productive.
You can add a Quick Access icon for adding a footnote, and stay on the EndNote toolbar when writing.
In Word, click the Customize Quick Access Toolbar icon at the top of Word.
Click on More Commands.
In the command list, scroll down until you find Footnote.
Click once on Footnote to highlight it.
Click on the Add button.
Word will now have a Quick Access icon for adding a Word footnote.