Content > Release
Move your mouse over the post preview you want and click Edit to select
Publish now 🔽 > Save as draft choose this option
The release moves to Drafts
Content > Release
Move your mouse over the post preview you want and click Approve/Reject to select
In the edit window, click Reject to select
The post will now be moved back to Drafts automatically
ATTENTION: It's enough for only one person to reject the post for it to go back to drafts.