I do not think it can be done on the LCM on the E53 X5. I did however find a iBus module that looks like it will be fun to play with. Modlight2. A simple 3 wire connection in the rear by the cd changer area or anywhere you can pull 12V, GND and iBus. Modlight2 does offer 3 4 and 5 blink one touch turn signals along with a long list of features to play with. I ordered it and will report back.
https://modbmw.com/modlight/
https://www.youtube.com/watch?v=RQAJAA7rqAk