Bump

My apologies for the late response ... (my daytime job keeps demanding so much of my time )

You're looking for quite a few changes ... and I'm not in the position to build a setup to test, but I'll try to see what I can do to help.

As for controlling with a potentiometer; what should this influence? Speed? Color? Eyesize?
For Color; what kind of change are you looking for? Change the entire color for the whole bounce loop? Or transition colors from color 1 to color 2, static or during the loop?

I think we need a slightly better definition of what you're looking for. (not intended as criticism, just me not quite getting the details  ). 

I have employed the help of someone from Fiverr to try to get this sorted out of for me,  I do appreciate your response and the original code.

What I am trying to do is change the color, speed, eyesize, brightness & width of used leds (my strip has 43 LEDs and want to shrink the scanner down to 23 used LEDs) on the fly from 5 different potentiometers input into arduino uno. I know I can change all of these values within the code, except I havent figured out how to change the amount of trailing LEDs.

That a great idea (Fiverr), I've used Fiverr in the past for other purposes, but it most certainly is a great way to get this done.

Adding trailing LEDs would indeed come with some extra code. I'd have to play a little bit with it though to get that correctly implemented. An initial thought would be something like this:

void loop() {
  CylonBounce(0xff, 0, 0, 4, 100, 50, 4);
}
void CylonBounce(byte red, byte green, byte blue, int EyeSize, int SpeedDelay, int ReturnDelay, int TrailSize){
  for(int i = 0; i < NUM_LEDS-EyeSize-TrailSize-2; i++) {
    setAll(0,0,0);
    setPixel(i, red/10, green/10, blue/10);
    for(int j = 1; j <= EyeSize; j++) {
      setPixel(i+j, red, green, blue); 
    }
    for(int j = EyeSize; j <= EyeSize+TrailSize; j++) {
      setPixel(i+j, red/10, green/10, blue/10);
    }
    //setPixel(i+EyeSize+1, red/10, green/10, blue/10);
    showStrip();
    delay(SpeedDelay);
  }
  delay(ReturnDelay);
  for(int i = NUM_LEDS-EyeSize-TrailSize-2; i > 0; i–) {
    setAll(0,0,0);
    setPixel(i, red/10, green/10, blue/10);
    for(int j = 1; j <= EyeSize; j++) {
      setPixel(i+j, red, green, blue); 
    }
    for(int j = EyeSize; j<=EyeSize+TrailSize; j++) {
      setPixel(i+EyeSize+j, red/10, green/10, blue/10);
    }
    showStrip();
    delay(SpeedDelay);
  }
  
  delay(ReturnDelay);
}

I have not been able to test this, by lack of having an Arduino + LED strip available, so it might not work as expected.

Would you mind posting the result? (I'd understand if you'd rather not)

I will post results when completed. I'll give your idea a shot in the mean time.

Cool - thanks !