It doesn't help that the manual is unclear and describes things inaccurately. 13, 14 and 15 are always lit in "Function" -> "Pad Action" mode. 13 gives you the choice of All or Cur, 14 gives you the choice of Int, Ext, or All, and 15 gives you the choice of b1, b2, b3, b4, or All.
To get an effect on one bank, I made sure I am in that bank, make 13 Cur, 14 Int or
All, and 15 b1 since I was just wanting Bank 1 to be effected. I don't know what other combinations do yet, I'll let you know