Question is in the title. I find this would be useful to me because I can't apply a mirror to an object that has shapes keys. If I could mirror annotations, I'd be able to at least trace the outline of an objects side and move vertices according to the mirrored side.
For instance, I am making eye lids for my character. In Front Orthographic view, I can use annotations to mark what looks symmetrical to my eye. It got me wondering if blender has a function to mirror the annotation instead. Maybe there is a plug in that does this?