Yaseen is the Heart Of the Quran:
Prophet Muhammad (PBUH) said in one of His hadiths in the following way:

“Surely everything has a heart, and the heart of the Quran is Yaseen. I would love that it be in the heart of every person of my people.” (Tafsir-al-Sabuni Vol.2)

From this hadith of Prophet Muhammad (PBUH), it becomes clear that like all other things that have a heart, the Quran also has a heart and it is Sura Yasin. From this a person can only guess the importance of Yaseen, as if a single word from the Quran carries great reward then the heart is surely to reward