Multiple invoice payment
https://apps.odoo.com/apps/modules/12.0/gts_multiple_invoice_payment/
On payment screen auto fill all unpaid customer and contact's invoices.
Easily lets you assign full or partial payment to the selected invoices.
Shows Assigned and balance amount on payment screen.
As you can see there are 4 invoices for Camptocamp.

Now we are creating a payment for Camptocamp. All 4 due invoices are auto filled here upon customer selection
Now we are creating a payment for Camptocamp. All 4 due invoices are auto filled here upon customer selection

Now we are making payment of $7000, Date wise auto amount is assigned to the invoices.

However you can assign amount manually to invoices as shown below.

Payment is confirmed.

Now as we see here payment is properly assigned to the invoices.
