Unfortunately, it is not possible to drag and drop emails (Mail.app) into the notes field of an existing task. Instead, a new task is always created. (In addition, the links to emails are displayed in incorrect formatting.)
Am I doing something wrong here, or is there a better way to achieve my goal?
An additional comment on this topic:
It would be very convenient if, instead of the path to the email, a text link were automatically generated in the note field („show in mail“, for example).
This is already common practice in programs such as BusyCal (and others) and ensures a tidy appearance.