Participant add/remove controls during Promotion Request CREATION

I feel like I’m missing something that is probably right in front of me.

How does one control the ability to Add/Remove participants during creation of a Promotion Request?

Unlike an Activity that has the Role Setup tab, I do not see one that would allow me to control this during the initial creation of the Promotion Request in the Create New Promotion Request wizard.

Thank you for your response!

-Vaughn