Brad Orluk‌ wrote a blog announcing the new feature with details on how to use it

I was unable to find the accepted solution or blog post mentioned.

Re: Nintex for O365 w/f schedule not running

I had a Nintex for Office 365 daily scheduled site workflow that wouldn't start - site feature was activated, workflow was fine if run manually, but schedule never started it.

I deactivated and reactivated the site feature to elevate (Workflows can use app permissions) and set the workflow start to yesterday to cover-off any timing issues on the first run. All good after that.

Posting for others that may be seeing this issue and unable to find the solution or blog posts mentioned.