How do I add a child record without saving the parent record?

i'd like to be able to add child records to a parent record without having to save the parent record that i'm currently editing.

i'm using a meeting tracker app and would like to be able to add action items while i have the main meeting record open. the goal is to have a button that i can press from the meeting (parent record) that will open a new window for quick editing, then i can edit the child record quickly, then save the child record and go right back to the meeting record to continue the call and continue adding child records as needed.