Continuing the discussion from One Payment for multiple Invoices:
Some user/party manage the payable/receivable globally instead of line per line for the payment.
Currently it is possible to do it but it requires manual operations and computations.
Define on each party how their payments must be managed: per line or globally.
Add a view which shows the balance amount (to pay - to receive + running payments) for parties that are managed globally. The computation is based on a contextual date (to allow payment in advance). From this view, it is possible to create payments for the selected lines (like for current move lines).
The current view lines to pay should not show those linked to a party managed globally.