In Mail for iPadOS (also in iOS?), you can long-press any text in the email - not just in the subject. When I choose Reminders, that app opens with a new-reminder box that includes the words of the email’s subject line, a text box for optional description text, AND a link back to the email. Once you choose “Share”, the Share window opens, with one of the (many) apps offered for sharing is Reminders. On my iPad, in Apple Mail, when I long-press any word in the subject of an email, Mail opens a selection bar with the “Share” option, among others. This also works natively in Apple Mail for iOS !!!