Dynamics NAV gives us many examples of advanced pages where some kind of subpage is embedded into a main page, offering additional information related to the entity being viewed. Different documents are always based on this principle: the main document page displays the document header, while various types of subpages represent document lines and detail the entities related to the document, such as customer, vendor, item, fixed asses, and so on.
In the next section, we will create a document page presenting the lease contract, and add contract lines in a subpage. In a separate subpage, we will report the current payment balance to the customer.