Header and Line View allowed in custom data source (BPA)

We are using BPA for our invoice print. We use the standard Receivables Data Source as Primary Source (with Billing Lines and Invoice Header View).

We have a Custom View as Supplementary Data Source, with display area Header and Footer.

We are looking at a way to group certain invoice lines for a particular transaction type (invoices coming from property management, where rent increases per year result in additional lines).

Can a Supplementary Data Source consist of only 1 Custom View, or can this have multiple custom views, for example one at Header/Footer level and one at Line level?

Ideas on how to group invoice lines on an invoice print using BPA are welcome. The lines to be grouped would have the same PN contract nr, currency, tax_rate, and a DFF field would indicate the description to print