It was further up the conversation - If you’re on the current stable (v3…) firmware, the file you need to modify is /usr/bin/mt1300_led.
The line you need to edit in the current stable is:
i2cset -f -y 0 0x30 0x06 0x3f
i2cset -f -y 0 0x30 0x07 0x7f
The top line is blue, the 2nd line is white (I think). Modify the last two digits to smaller numbers to dim the lights. I used 0x0f for both numbers.
On the daily (V4…) firmware, the file is /usr/bin/gl_i2c_led. You’ll need to add those two lines at the bottom of the file to limit the brightness.