The DRL’s are designed to switch off when headlights are on, there should be a harness available.
yes, that's what I need to know instead of damage the headlight wire to give signal to turn off the DRL, what else can also give singal to the harness to turn it off ?
IIRC: For the FD model, there was a separate fuse for the headlamps from which you could tap a signal.
But with the GD, and maybe the PD models, the headlamps and parking lamps are fed directly from a "smart junction box" which is collectively powered through a 60amp fuse. So, AFAIK the only route is to get your signal straight from either the headlamp or parker wires, as you already noted.