Are there verses specifically designated for certain purposes (such as protection, preservation, healing, or ruqyah)? Is this found in books on healing with the Quran? And what is the opinion regarding Shaykh Wasfi Muhanna's book "Al-Kanz" (The Treasure)?

There is nothing in the Sharia that dedicates specific verses for memorization, healing, or Ruqyah. Some scholars are of the opinion that dedicating verses for specific purposes without a Sharia-based proof is an innovation (Bid’ah). However, some scholars are more lenient regarding the dedication of verses based on experience, such as Ibn Taymiyyah, who used to recite the verses of tranquility (Ayat Al-Sakinah) during hardships and write specific verses for healing from illnesses. Therefore, whoever recites specific verses, emulating the experiences of the righteous, without believing that this was ورد (mentioned) in the Sharia, bears no sin. Nevertheless, adhering to what is ورد (mentioned) and Athar (narrated from the Prophet or his companions) is safer. The entire Quran is a healing and a mercy. Texts have been ورد (mentioned) regarding the فضيلة (virtue) of some surahs and verses, such as Al-Fatiha, Al-Baqarah, Al-Mu'awwidhatayn (Surahs Al-Falaq and An-Nas), and Ayat Al-Kursy. It is permissible to dedicate them for healing and Ruqyah.