Sub-Feature as a Push Button Property, need 2nd dialog to open

I would like to create an additional dialog displaying sub-features in my schema. 

The idea is to press a push button for the additional dialog to open. 

The schema does offer the ability under OPERATIONS to create a push button, but what about the METHODS.  How will the METHODS know about the sub-feature?

Are there anybody that can assist me in creating this?

Thank you!