Here is an easy way to do it.
Take apart the light switch. In one corner of the housing half, there is a small spring. Take that spring out, it's the return spring for the rotary switch when it's turned counter clock wise to turn off DRL and auto headlight. Put everything back carefully, there are tiny parts everywhere and make sure the switch position retainer is positioned correctly. Pay attention to the tiny pin for the dimmer switch.
Now when the switch is rotated CCW, it will not return to auto. The DRL and automatic headlight will stay turned off until the switch is turned clockwise.