Since you want a section in the middle of the document, you have to insert two section breaks, one at the start and one at the end of the range where you want your section.

To see the section breaks more easily, choose to show nonprinting marks.

With the "Filling in forms" type of protection, you can deselect the "middle" section so that it is left unprotected. Note, however, that many actions are not allowed, even in an unprotected section in a protected document.

Personally, I'm not using a Mac, but the commands you mention

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional