Sure.
So you have a form that adds an item to your sharepoint list. Let's call it Form1 and List1.
You also have a button that submits the form.
Your button's "OnSelect" property needs to be SubmitForm(Form1).
You also want to add more data to this sharepoint list item that your form doesn't ask the user for, am I right?
If so, you want the form to create the item, then when it has successfully created the item, to patch on some extra data from somewhere else that isn't the form, yes?
So you would select the "OnSuccess" property of form1.
And you would put:
Patch(List1,Form1.LastSubmit.ID,{column1: value1})
Where value1 might be anything.
Tell me more about the column you are wanting to add multiple values from a collection to.