Hmmm… Am I doing something wrong ? Or does this just not work on this switch ?
Using 7.11.2 on the CRS309-1G-8S+ the LED settings function does not affect the port LEDs. It does control the user and pwd LEDS. But all the port LEDS all stay lit when setting off immd or timed..
I could be mistaking but to my knowledge port leds can not be manipulated.
The only way would be to disable the port but I guess that’s not what you’re wanting to do just to switch of the lights 
The other routers I have worked with all switch off the port lights with this command. But this switch does not.
Other units I have worked with will go fully dark, no LEDs at all, with this setting..
I can manipulate the port LEDS if I do each one manually.. All the manual commands for each port on the LED menu work.. Like off/on and all the other stuff.. The only thing that does not work are these commands that affect the entire device.
Should I report this as a issue to Mikrotik ?