Multi-Step Workflows

I am trying to improve my business workflow. Currently, there are 4 boards for this workflow. Admins are responsible for PO-Project and Invoices. Project team will be in charged in Service Schedule and Pending Installation boards.

First, when “PO-Project” is received, it will trigger an automation to create an item in “Pending Installation”. After that, when the status in “Pending Installation” changed to Ready to Install, it will then create an item in Service Schedule. When installation is delivered, then an item will be created in Invoice board. This is an ideal workflow.

The thing now is, for a Project, there are different payment milestone. So, in “PO-Project” board, a new group will be created to record the payment milestone. The limitation is to not let the “Pending Installation” board having the price information, only status of installation is needed.

This will create a problem where in the previous workflow, when “PO-Project” is received, the payment milestone will not be created in “Pending Installation”, only a single item will be created in “Pending Installation”. Now, there will be multiple invoices to be issued by admins based on payment milestone. Then based on the previous workflow, there will not be a same name in the invoice board. Thus, the invoice created from "Service Schedule’ will need to be deleted after extracting the information needed from it. As the name is different from payment milestone name.

What I want is to combine the information created, so that the item will not needed to be deleted