You can't map two keyboard keys to the same parameter. Neither can you connect two MIDI events to the same parameter, or two event of the same type (OSC / DMX...)
But you can create a cue with the parameters you want. To do the the easiest is to
- select a cue cell in the cue bank (cues are from second row, first row contains scenes)
- press the cue bank Edit button (or Cmd+Shift+C / Ctrl+Shift+C)
- click the widgets corresponding to the parameters you want to store in the cue (ie: /medias/myMovie.mov/rewind)
- map a computer keyboard key to this cue
Then create another cue.
Does it solve ?