We are using PCS (Project control) module.
We maintain the standard routing and we copy the standard routing to the customized item in the Project engineeting module (copy standard product structure to projet, tipcs2230m000).

In the standard routing we often open several codes for one item.
The problem is that when maintaining production orders for those items (in the shop floor control tisfc0101m000 maintain production orders), if the project field is filled with data there is no option to choose a routing code.

I guess that when using a opening a production order with a project, the routing is taken from the customized routing.
Is there a way to use several routing codes for the customized routing (item)?

No there is not. A project assumes that you create the routing, custom for that item on that project. That is just the nature of projects. You will notice that project routings also do not have effective and expiry dates. It assumes that the routing is for the duration of the project.