Figured it out. Button/Dial Setting > Command Dial Setting > S.S.
Once I set the above I was able to change the shutter speed when T (Time) selected on the shutter speed dial.
I am evaluating a X-T5.
When the shutter speed dial is set to T (Time) the rear command dial doesn't change the shutter speed, it is set at 100. I'm wanting to set it at 30 seconds for a night shot. Any ideas why this is so or how to change it?