Google Drive apps and Docs app suite add-ons are getting a new home. Earlier in the Chrome Web Store, they'll soon be available on the G Suite Marketplace, which you probably never knew before. Find apps for business and productivity. Considering its purpose, add-ons that extend the functionality of utilities such as Drive and Docs are just as well-suited. All Drive add-ons and Docs Suite apps will be postponed "in the coming weeks." The Add-Ons option in your Documents toolbar also results in a new G Suite popup.
What does that mean for you? The odds are good, not much. Most of the apps you've already added from the Chrome Web Store will continue to work as before. If you used an app to create a template and its creator does not migrate the app to the Marketplace, the template will not work until it works. If you have developed an app that is affected by this change, you can list it on the G Suite Marketplace by 9th September.