Editing a tweet is something that many people have been waiting for a long time, although Twitter has always refused to offer something like that because it could tarnish the historical record of their network.
Keep in mind that Twitter is considered a content network, rather than a social network. Many people say great things on Twitter, and others share or save it for later mentions. If Twitter offered the ability to edit content already published, it would break the sense of the network and would make the controversial tweets being discussed lose their authenticity.
The fact is that for a long time a new option has been chewing, that of being able to do an undo during the seconds after publication. It is like a phase of possible regret that lasts a few seconds, enough to verify if there is any spelling error or if we do not want to regret the subject.
Now, using reverse engineering, it has been discovered that this undo time can reach 30 seconds, as Jane Manchun Wong shows on her Twitter.
Apparently, by interpreting the screenshots, Twitter is working on the ability to set the duration of the Undo Tweet timer to 5/10/20/30 seconds. It is also possible that you are working on a preview of a tweet.
It is important to note that the feature was discovered through reverse engineering to find hidden features and security vulnerabilities, so while it may appear as a feature in the future, there is no guarantee that it is.