[curt.clifton]

Originally Posted by SpiralOcean

This is a link to the OmniFocus plist file, the preference file. There is no current user interface for this switch.

If you clicked on it and want to set it back to showing groups/projects in the context, here is a link for that as well.

omnifocus:///change-setting?ContextM...wsParents=true

The ability to change settings using URLs was added in 1.8 and is documented in the release notes. As SpiralOcean points out, currently you have to mine the plist to find all the hidden settings.