Small changes in an asana also change the stretch. If you pull your arm to the side, you stretch the entire side of your body.
Sometimes I bring the arm behind the back to the thigh. The hand rests on the thigh and supports the body to turn up and pull the shoulder back.
From trikonasana you can easily bend one knee and then practise utthita parsva konasana. This is a different way to get into the pose than in classical Ashtanga where you first bring the legs into position and then the upper body.
If you stretch both arms out to the side, you need to balance better.
If you keep thinking about variations, you will begin to understand the postures better. The mind remains alert. You interrupt the autopilot mode.
You can practise more difficult variations at the beginning of the exercise. This insight is a game changer.