Now it looks like Twitter is working on something similar codenamed “Flock” according to Alessandro Paluzzi. Basically with this Flock feature, which apparently won’t be the final name, users can create groups of up to 150 people to include in their “flock”. This means that when you post a tweet, you can choose to only have people in that group to see it.
https://twitter.com/alex193a/status/1484377272731590656
So similar to what Facebook and Instagram are doing, this allows Twitter users to have public profiles but still post more personal things that maybe a random stranger on the internet won’t be able to see. Based on the way the feature is currently setup, Twitter says that users can add or remove people from this list anytime and they will not be notified, so if you have a falling out with one of your friends in your flock, you can remove them and they won’t know about it.
Right now, the only way for Twitter users to keep their tweets from being seen by strangers is to make their accounts private so that they get to choose who can follow them and who gets to see their tweets, so this “Flock” feature could help give users a bit more flexibility.