Before SSL 2.0, you could modify an XML to override the buttons/knobs on a controller with Native Support in Serato Scratch Live.

After SSL 2.0, it was nearly impossible until I figured you could hijack the MIDI input using the FREE MidiOX software or Bome's MIDI Translater. You would leave the MIDI output alone to get the HID and LED button lights support in SSL.

I was able to hold down Effect 1 + Jog Wheel for the Dry/Wet. Hold down Effect 1 + turn Parameter Knob to divide/multiply the beat by 2.

I just recently got the Back Button (tracks to crates, then expand/contract crates), PM Push (crates to tracks, then load song) and delete Cue Points working correctly thanks to radikarl.

If you have a Mac, you could try using MidiPipe.

MIDI-OX

Step 1: Download MIDI-OX (FREE) and install. http://www.midiox.com/
MIDI-OX 7.0.2 (917K 17-JUN-10) Download

loopMIDI 1.0.1.7

Step 2: Download loopMIDI (FREE) 1.0.1.7 and install. http://www.tobias-erichsen.de/loopMIDI.html
Download

Step 3: Configure loopMIDI

MIDI-OX MIDI Devices

Plug in your DN-HC4500. Go to Options/ MIDI Devices.../
Under MIDI Input, select 1)DN-HC4500
Under MIDI Output, select loopMIDI Port and select OK

That's it! Open up Serato Scratch Live and you will be able to assign the buttons and knobs to whatever you want.
I will be posting my mapper later that features:
* Jog Wheel Support
* Back Button Support (Goes from Tracks to Crates, then Expand/Contract)
* Parameter Knob Support (Goes from Crates to Tracks, then loads)
* Delete Cues (Hold Down Flip + Cue to Delete a Cue)
* Flip + PM Knob Rotate = Loop Move
* Flip + PM Knob Push = Loop Roll
* All 3 effects and SuperKnob control
* Censor Support
* Etc.

MIDI-OX-Data-Mapping

Trying to hide the MIDI up for the Cues. See reason below...

Step 4:

Download my XML and PDF to show the assigned buttons

Stay Tuned... I'm not finished. I'm running into problems with the Cues. When you push it, it activates the cues. However when the cue button is released, it activates the cue again. Weird.

Mac

MidiPipe

Step 1: Download MidiPipe for FREE HERE and install.
MidiPipe can be useful in a music studio or live on stage to route, map, filter, convert, display, input and output MIDI messages in real-time.

Set MIDI In

Step 2: Select Input in the Tools drop down. Drag and drop Midi In from the left 'Tools' to the right 'Pipes'. Serato DJ will disable the controller if Options "hijack" is checked.

Set MIDI Out

Step 3: Select Output in the Tools drop down. Drag and drop Midi Out from the left 'Tools' to the right 'Pipes'. Midi Output should default to MidiPipe Output 1. Under Options, 'Pass Through' should be checked.

Serato DJ MIDI enabled

Step 4: You are now able to customize your controller.

LineIn for Mac

LineIn enables the soft playthrough of audio from input devices. In simpler terms, you can use LineIn to play sound through a microphone or any other device plugged in to your Sound In port. If you need to input audio from an external device, recreating OS 9's "Play input through output device" option, then LineIn is perfect for you.