Randy, thank you for the guidance. Hopefully below I'm offering enough information, without being to verbose.
100% transparency, I am NOT a programmer. I am a network admin that is a script kiddie to get where I need to be and get myself into trouble.
My current "design" is a BrowseGallery with the HeaderTable Source.

When you click a record there it brings you to a DetailScreen with the HeaderTable Source. Also, when you click the Browsescreen record, it sets a RequestID Variable.
Navigate(DetailScreen1, ScreenTransition.None);
Collect(SelectedRecord,BrowseGallery1.Selected);
Set(RecordSelected,BrowseGallery1.Selected.RequestID)

From here you can Edit the Header record (this will eventually be home to workflow processing as well for approvals)
You can also click the Line Detail button which opens a Line Detail screen with a new datasource Req_Detail that contains line items of parts for order.
This page has two controls on it. A view table and a form.
When you click a record in the Table it open the form for editing of that record.
The table opens using the Variable set before at the header screen.
SortByColumns(Filter('B&G_Req_Detail',NewReqID=RecordSelected),"field_1",Ascending)

Form Data is set with:

When you click the New record button it calls the NewForm() function. I also create some Variables that were intended to set the Next Line number and requestID number, this was how I planned to tie the Header and Detail information together.
I also intended to add things like username, Now() and other default values to the Form.

NewForm(Detail_Edit);
Collect(
DetailRecord,
DataTable1.Selected
);
Set(
DetailRequestID,
DataTable1.Selected.RequestID
);
Set(
DetailLineNum,
LookUp(
SortByColumns(
Filter(
'B&G_Req_Detail',
NewReqID = RecordSelected
),
"field_1",
Descending
),
NewReqID = RecordSelected,
LineItemNum
)
);
Set(
DetailNextLineNum,
DetailLineNum + 1
);
Cancel button just calls the ResetForm() function.
Erase calls the Remove('B&G_Req_Detail',DataTable1.Selected) function.
Save calls the SubmitForm() function.
I'm having a hard time figuring out how I would link the header and detail data together without some sort of a key (unique id per Instance of Header, to detail.
Attached is the sample data I'm using.