Problem: How to dispaly parent post featured image conditionally
Solution: you can use [wpv-conditional] shortcode to dispaly conditional output.
You can find proposed solution with the following reply: https://toolset.com/forums/topic/check-if-page-has-parent-and-use-its-featured-image/#post-406904
This is the technical support forum for Toolset - a suite of plugins for developing WordPress sites without writing PHP.
Everyone can read this forum, but only Toolset clients can post in it. Toolset support works 6 days per week, 19 hours per day.