If you had your Facebook or Twitter account signed into from MacOS High Sierra and used the widget in the Notification Center to send updates and Tweets, bad news is coming in MacOS Mojave. The ability to add these accounts and the Social widget in Notification Center have been removed.
If you go into Settings>Accounts, you will note that you no longer have the ability to add these social network accounts to your Mac and the Social widget has been completely removed from Mojave.
It probably isn’t overly surprising given the way that Twitter has been handling their APIs with 3rd party apps, of which MacOS would be considered one of them, and the changes Facebook is making in their own security processes. Still, for those who liked the simplicity of sending a Tweet from a widget, the feature will be missed.
If you open up the Accounts settings in Mojave, you will see you can still add a wide range of mail accounts, including AOL (why?!) and, as reported earlier, you can add 2FA enabled Microsoft Exchange accounts now too.
So for those on Mojave, if you want to post something on Facebook or Twitter, you now have to go to the respective sites.