Problem: The issue here is that the user wanted to auto delete posts based on a criteria
In order to achieve this you will need some job that will run to check the posts for the checkbox that is selected then proceed to delete it.
Unfortunately i'm not able to assist with this as it fall out of the scope of our support forum.
What I recommend that you do is to contact one of our contractors to see if they can provide a solution for you. https://toolset.com/contractors/
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.