This command will turn the blue LED to MicroSD card access:
echo mmc0 > /sys/bus/platform/drivers/leds-gpio/gpio_leds/leds/blue:heartbeat/trigger
and following one will turn it off completely:
echo none > /sys/bus/platform/drivers/leds-gpio/gpio_leds/leds/blue:heartbeat/trigger
To execute this code automatically at each startups, just put it on a text file and save it as \userdata\system\custom.sh
I hope this setting will be integrate into the GUI because the flashing LED is really annoying😵