Save chatter posts as drafts
Save chatter posts as drafts: With the winter’19 Salesforce release, unpublished chatter posts will be as a draft. This feature is available in Developer, Contact Manager, Group, Essentials, professional, Enterprise, performance, and unlimited editions in lightning version.
To turn on this option in your Salesforce organization, Go to chatter setting -> enable the Allow drafts checkbox under Drafts post section.
To know more about this refer this URL: https://releasenotes.docs.salesforce.com/en-us/winter19/release-notes/rn_chatter.htm?edition=&impact=