How to add planning resources to a planning resource list already attached to the Project

Hello,

The customer has non-central planning resource list.

Planning resource list is already used in 1000+ projects.

Now there is a need to add 10 planning resources to the planning resource list so that they will be available for cost budget line.

Since the planning resource list is already attached to the project and used, we can not change the planning resource list setup from non-central to central.

Is there any API to update the planning resource list attached toa project to add additional planning resources to it.

or any other method or suggestion.

Regards,

Rajiv