Hey, I did not see this until just now, but eric is correct. The controller tab was removed and instead we have project wide “port” settings for DMX so you don’t have to set them per library. You can then select which port you want to use in the library. This will continue in UE5 and there are some expanded settings for locally over-riding the IP addresses, etc… through command line.
There is a larger DMX thread in Unofficial DMX in Unreal MegaThread. 4.26+ - #90 by steolepanda