HI,
I did it using the BT embedded on an RPi 3+. But it should work in the same way with an RPi 4.
It takes a bit of time, because you have to find out the codes to be sent to the BT controller of the LED, but at the end it is working.
For the moment I have created a simple card with some buttons to drive the main commands on the LED…
I am going to make it nicer with the custom button card.
The buttons are connected to scripts and the scripts contain shell commands to the BT controller like this…
balcony_led_on: gatttool -i hci0 -b {{ mac_addr }} --char-write-req -a 0x0009 -n cc2333
You will have to find the mac_addr of the BT device, the UID (-a) of the function and the command to send for the specific operation (-n). These are specific for each device.
Good luck. 