No, you cannot. You can only have one set of credentials per platform per organization in your CELUS (there has to be a unique combination of organization, platform and COUNTER version, therefore, you can have credentials for the same platform for COUNTER 4 and COUNTER 5).
CELUS will not let you save duplicate credentials (same platform, organization and COUNTER version as you already saved before).
If for some reason you have multiple credentials for one platform, you will have to Create a custom platform and input the secondary credentials there.
