Hi @Hildi_Pardo
You are right that there is a difference between being an Observer, and having an Observer role in a particular course.
However, I believe that what makes a user and Observer is being linked to a student. There is not really anything different about the user account itself being given to a staff member, or being given to a parent.
Some schools allow self-registration so that parents can create their own accounts with local Canvas credentials rather than using school SSO credentials, but the user accounts themselves are not really different, and some schools set up counselors, advisors, etc. (who have Canvas accounts automatically created, just like students and faculty) as "observers" for the students assigned to them, very similar to what @paula_d_levy wants to do.
A user can be paired with a student by the administrator, or by using a pairing code generated by the student (or the admin?) which is not course-specific.