Since you are using a built-in header, you get the same content control in both; that's why typing a title into one header would also reflect in the other header. Carefully select the "type the document title" prompt in the odd header and press Ctrl+X (cuts it to the clipboard). The border should still remain in the header. Now simply type in the title you want. Repeat for the even header.

Headers and footers are always greyed out in Word when the insertion point is in the main body of the document; similarly, when a header or footer is active, the main body of the document appears greyed out. But, as you probably have noticed, it doesn't affect how these areas actually print. If you find this annoying, convert the document to PDF before distributing it.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional