Desktop version: Right now you can use your left hand to tag a reference with I E and M but you need the right hand to move the cursor.
Could you add the option in settings to automatically move one down once the I E or M key are pressed?
Could you also - for those who don't want to move one down automatically - offer the option to re-map a key so it works as the down cursor? Examples are one of the function keys (F1-F6), the ~ key or the spacebar
Have you tried the page down key?