The Apple IIe's 20-line LIST routine (it begins at address $FE5E) is not
supported in the Apple IIGS.
In the Apple IIGS, a similar location remains a part of the disassemble LIST
routine. It is $F8D0, the INTSDP Display disassembled instruction routine,
which displays one instruction pointed to by the program counter. (The $F8D0
routine is looped through 20 times in the Apple IIe LIST routine.) $F8D0 can
be used in a similar routine on the Apple IIGS.
You may wish to review the Apple IIe routine in order write your own LIST
routine. For further information, see the Apple IIGS Firmware Reference
Manual and the Apple IIe Technical Reference Manual.