Really quite simple...why doesn’t Canon allow the master flash to be assigned to a group? It would make working with a on camera master flash and a remote slave easy to switch the contribution of light from each source. If I am reading the manual correctly the only way to do this right now is adjust the FEC on the camera/master flash and set a different value for the slave unit directly on the Slave. This isn’t that hard but it sure seems like it would be easier to make the master flash part of group A and the space group B and just adjust the ratio.
Sorry for the beginners question I’m just trying to understand everything these flashes can do. I just realized that the 430ex III-RT can be a radio master! I guess I was use to the old optical days and when the 600ex came out it was probably the only way to do radio master.