No.
Unfortunately although some would love to have this functionality, it would complicate the UI and the work flow. It would break a number of things including the ability to sync this information with the various different clients we support (CalDAV, iCloud Reminders, Toodledo etc).
Article ID: 460
Created On: Wed, Jan 27, 2010 at 2:04 AM
Last Updated On: Fri, Sep 19, 2014 at 8:32 AM
Online URL: https://www.2doapp.com/kb/article/can-i-nest-a-project-inside-a-project-or-a-checklist-inside-a-project-checklist.html