Annotation groups allow control over the visibility of subsets of the total set of annotations. To demonstrate this, begin by creating a model and running a simulation on it. Then:
Create three annotations, such as a mesh annotation and an electric and a magnetic field annotation. Make sure all three are visible in the Primary Group of annotations in the Structure browser. Make sure the Primary Group itself is visible also.
Create two annotation groups. Notice that for each Annotation Group you create, a node is added under the Annotations node of the Browser.
Add a reference to the mesh annotation to each of the two annotation groups. Add a reference to the electric field annotation to one of the two new groups, and add a reference to the magnetic field annotation to the other one.
Note that you can control the visibility of each of the annotations in the Primary Group and in each of your user-created groups. You can also control the visibility of the whole group. Turn off the visibility of the Primary Group, and turn off the visibility of both of the user-created groups. No annotations will be visible. If you turn on the visibility of first of your user-created groups, the two annotations referred to by the references in that group will become visible.
If you turn visibility of that group off, and turn visibility of the other user-created group on, the two annotations referred to in that group will become visible.