code: protected static boolean setCustomForDefaultClient(String profileName, String pathName, Boolean isResponse, String customData) {
          try {
              Client client = new Client(profileName, false);
              client.toggleProfile(true);
              client.setCustom(isResponse, pathName, customData);
              if (isResponse) {
                  client.toggleResponseOverride(pathName, true);
              } else {
                  client.toggleRequestOverride(pathName, true);
              }
              return true;
          } catch (Exception e) {
              e.printStackTrace();
          }
          return false;
      }
docs: set custom response or request for a profile's default client, ensures profile and path are enabled
  
  @param profileName profileName to modift, default client is used
  @param pathName friendly name of path
  @param isResponse true if response, false for request
  @param customData custom response/request data
  @return true if success, false otherwise