Twitter has introduced a Bookmarks feature. Users have to click the Share icon under the Tweet and select 'Add Tweet to Bookmarks'. To retrieve the bookmarked tweet users will have to tap 'Bookmarks' under Profile.
According to a blog post by Product Manager
In her blog post, Jesar Shah said, “Today’s update makes sharing better, too. With our new “share” icon on every Tweet, you’ll be able to bookmark a Tweet, share via Direct Message, or share off of Twitter any number of ways. Because we put all sharing actions together in one place, it’s easier to save and share privately or publicly — in the moment, or later.”