Multi-part tweetstorms are a staple of Twitter, for better or worse, and the social network wants them to be as easy to write as possible. After months of testing, it's adding a thread feature that simplifies creating and posting a series of tweets. The composer now includes a "plus" button that lets you tack on additional tweets, with whatever you've written before still visible to help guide your train of thought. And when you're ready, you can post everything at once -- no more leaving people hanging while you write the conclusion to your thrilling saga. You can add posts after the fact if you need to write an epilogue.