Either define your own custom keys or overload the global PlayerControl function or the object's ObjectControl function to catch these controls.

In the clonk script:
public func ObjectControl(int plr, int ctrl, int x, int y, int strength, bool repeat, bool release, ...)
{
  if(ctrl == CON_Interact && !release)
  {
    Message("Space was pressed.");
    return true; // return true to overload normal key handling
  }
  if (ctrl == CON_Contents && !release)
  {
    Message("E was pressed.");
    return true;
  }
  if (ctrl == CON_QuickSwitch && !release)
  {
    Message("Q was pressed.");
    return true;
  }
  // Normal key handling (movement, etc.)
  return inherited(plr, ctrl, x, y, strength, repeat, release, ...);
}


You can look up these names in the global System.ocg/PlayerControls.txt file here. You can also have your own System.ocg/PlayerControls.txt in your scenario to define extra controls on any key.