Multi-customers project and sales orders

Good morning,

my purpose is to create a multi-customers project and assign it to sales orders for different customers. Then, invoice the sales orders to the related customers.

I've checked the documentation about "Multi-Customer Projects" but this process is not explained.

I'm not using Point of Sales.

I've created and released a multi-customers project. Now I want to create a sales order and I want to assign the item to such project but it's not visible in the list. The item type is "Service - fixed price (project)".

Documentation says that "When you create a sales order with a standardized service or a service-related expense, you can add a task of the multi-customer project to the sales order item". Could you please give me more details about the scenario above? In particular for "Standardized service", which item type should I use?

How can I achieve this? Did you face similar scenario?

Thank you!

Rossano