I am wondering if anyone has ever heard or knows anything about this practice of mindfulness where you are aware of conceptualizations as they arise and once they arise and you are aware of them you simply let your mind relax? Not sure if anyway associated with Guru Rinpoche or Nyingma but if you know anything about it please let me know.
Yes - you can find these instructions not just in Tibetan Buddhism but in Zen Buddhism as well. This is actually a kind of union of shamatha and vipashyana as this combines calm abiding with practicing/cultivating wisdom. With the relaxation emphasized people might say this is more Dzogchen flavor (for example Sogyal Rinpoche taught on this practice at length after HH Trulshik Rinpoche's teaching in September or so 1999) but it's not Dzogchen.
Actually this practice per se is also known in Vedic oriented meditation.
_________________Kirt's Tibetan Translation Notes
"Only you can make your mind beautiful."
HH Chetsang Rinpoche