She said, “Hi Twitter! Many of you (especially in Japan!) have said you’d like to be able to easily + privately save Tweets for later. Right now, people bookmark Tweets by liking, DM-ing to themselves, or Retweeting. But this could be easier.”
According to the video shared by her, the add to bookmark option will be available by clicking on the three dots. All the tweets that you bookmark can be viewed under the profile section on the Settings page. The tweet also said that the users will be able to “privately save Tweets” implying that the users whose Tweets you bookmark, will not be made aware of the action.
So far, there is no information about when this feature will be rolled out. The bookmarking feature comes soon after Twitter said that it is soon going to relax its 140-character limit and extend it to 280 characters — double the existing cap — in most languages around the world.