Max usb current will not save

Hi. A complete newbie to osmc and raspberry pi. My setup is: raspberry pi 2 model b running osmc 2015.12-3. I I’m trying to connect wd passport 320gb. I just bought new power adaptor 5v 2a.
I have tried to change max usb current setting in myosmc/pi config. Initially little square is lighted up but when confirming with OK at the bottom of the screen it goes back to main my osmc menu. When I open pi settings again usb current option is still greyed out. is anything else can be done?

This bug was located in the PiConfig module the other day. We’re testing changes to ensure that it’s all resolved prior to pushing to the masses.

Are you able to SSH into the pi and edit config.txt manually? It’s not terribly difficult to add the line.

Thank you for a prompt reply. Never used ssh before, so did it easy way (for me at least). I took sd card out plugged it to different pc and edited config.txt manually. My external hd was discovered instantly. Thanks.