A family of Microsoft word processing software products for creating web, email, and print documents.
The Win 10 version is interesting, but not relevant for this specific problem.
If you look in the link that Suzanne provided it says that as of August this year the feature has been released to "Monthly Channel (Targeted)". This is one way that MS controls distribution of features.
In any Office application go to File menu > Account command. Look under the bundle name it will display the "channel" you are on. If you are not in the designated channel, you won't have the feature, yet.
This article provides an overview of the various channels:
https://docs.microsoft.com/en-us/DeployOffice/overview-of-update-channels-for-office-365-proplus