Can you clarify some more–is the purpose to add a new row when you click submit or edit an existing row? Your description sounds like you are adding new rows, but I see you are using an edit form to edit an existing row.
In relation to this thread as well as your other thread, will users primarily be using mobile devices or a PC when using your app? Certain things including form buttons and the plus button on a collection will appear differently depending on the screen size. For mobile devices, you could build a custom form and add buttons the way you want, or possibly use a form container instead of a form if your goal is to add instead of edit rows.
Just need to understand your goal to point you in the right direction.