This is pretty easy but not real intuitive.
Create your plus button.
create a boolean, true/false, field in your main data source.Default true
Set your repeating table conditional formatting to hide when the field is true
Set conditional formatting on the plus button to hide when the field is false and that when clicked it makes the field false
Add a minus button right next to the plus button.
Set its conditional formatting to hide when the field is true and when clicked it makes the field true
That should toggle the visibility of your table records and have each button only visible when needed.