In the Opportunity fine tuning under the option to maintain Involved Item parties, only one party role "30 - Competitor" is available.
SAP Cloud for Customer
Reproducing the Issue
1. Go to the Business Configuration woc.
2. Select the Implementation Projects view.
3. Select your relevant Project or Change Project.
4. Select Open Activity List.
5. Search for the Activity: Opportunities.
6. Select the Link: Involved item parties.
Result: role "30 - Competitor" does not work as per your expectation.
On opportunity item, only z-parties with role category "competitor" are supported today.
This is expected behaviour/ not currently supported.
Related KBA: 2745355 - Error 'Please report an incident. Party instance is inconsistent.' When Trying To Add Party Or Competitor To An Opportunity
KBA , LOD-CRM-OPP , Opportunity Management , Problem