Hide resource organization in LOV when creating contracts

Summary:

We have created a resource organization hierarchy.

General resource organization is a a parent and has type 'service organization'

IT, Finance etc. are it's children with type 'contracts organization'

Currently when a user creates a contract and adds a resource organization they can add all organizations including the parent.

Content (please ensure you mask any confidential information):

Can we somehow restrict adding the parent to a contract? We have only set it up to facilitate a resource load.

Version (include the version you are using, if applicable):

23C

Code Snippet (add any code snippets that support your topic, if applicable):