"claimsParameterSupported" should not be related to what you try to achieve (if I understood you correctly). This parameters enables support for [this part of OIDC spec](https://openid.net/specs/openid-connect-core-1_0.html#ClaimsParameter)(a way to request specific claims instead of refering to them via scops)
1. You need to make sure all your custom attributes have "Usage Type" set to "OpenID" and assigned some "oxAuth claim name".
2. Then you need to add these attributes to some scopes at "OpenID Connect -> Scopes", either to a pre-packaged one, or create a custom scope as well.
3. If you need your client to request for this scope during dynamic registration, make sure you'll set "Allow for dynamic registration" flag for this scope.
Then it should boil down to sending a proper dynamic registration request to Gluu.