Jos.,
You most likely have an R4s. It shows the shutter speed that's set automatically in the viewfinder, or the shutter speed you should set yourself in manual mode, but the shutter speed set on the shutter dial doesn't show in the finder in manual mode. (Hope that's clearly written.) The R4sP has what I refer to as a full information viewfinder in manual mode because you see the aperture, the meter's recommended shutter speed, and the shutter speed you've set. The manually set shutter speed is missing in the R4s finder. I have an R4s, and that missing finder information is one reason I prefer another body, as I shoot in manual mode. (Well... I have used autoexposure about three times since I got a body that would do it in 1979.)
The shutter speed for electronic flash synch is the X between the 1 and B on the shutter dial. If you have the correct cord to connect the Metz 45 CL-4 to the hot shoe, the flash should set the shutter speed properly. I believe that speed is 1/100 second, but I don't use flash much, so I'd have to check that. You have two mechanical shutter speeds on the R4s, indicated by the orange markings, the B and the 100 beside it. These operate without the battery. If you do long exposures in very dim light, take out the battery and use B. The red finder LEDs can leak down to the film with fast film and long exposures.
Hope you can shoot some of your favorite slide film soon. It's nice to see exactly what the lens can put down on film, unadulterated by subsequent reproduction steps.
Lee