I've noticed that random folder advance does the same thing weather you use (combo left, or short left, short right) and (combo right or short right, long right)
It also goes to a random directory when you double left.
I propose the following changes:
-double left, last track of previous dir (not random)
-double left, then right(at any time during the previous track) - first track of current dir
-short left, long left - previous dir(not random)
-combo left - previous dir(not random)
After a double left, i am unsure if the file should advance to the current dir or go to a random after completion of the last track. I would presume random, but think it should be discussed.
All other behaviors should stay the same. To me, the changes would make more sense.