About Security Marking
You can designate an annotation as a security marking. You can designate only notes and symbols that are flat-to-screen, unattached, and standalone as security markings. You cannot copy such annotations. Annotations designated as security markings have the following characteristics:
Always visible whenever the model is viewed in a product that supports the security markings.
Listed at the top of the detail tree in an active combined state.
Shown by an icon in the Detail Tree and Model Tree.