Since the front print bed leveling screw head is covered by the print bed, you can screw on two M5 nuts onto to bottom of the front level adjustment screw and tighten the two nuts against each other.
Now, you can hold the leveling screw with the bottom of the two nuts to loosen the lock nut. Once the lock nut is loose, you can use the interlocked two nuts to turn the level adjustment screw with the print bed in place.
No need to tighten the lock nut back up. There is enough tension / friction from the spring to prevent the screw from turning by itself.