We are looking to use the out of the box attribute 'Affiliated Project' in the Modern UX. The issue is that we cannot add an API attribute ID to this field.
Release : 15.7.1
Component : CA PPM PROJECT MANAGEMENT
The Affiliated Project and Company Code fields were added to Modern UX in 15.8.0. So unfortunately they won't yet be there in 15.7.1.
You could try using a custom attribute type Calculated that would copy this information.
We recommend upgrading to 15.8.1, this feature and other new features will be in New UX.