If I select the annotation, then Edit Vertices, I see the line(s) displayed.
Then, if I right click on a section of the line and change to (or insure is set to) Circular Arc, then I can just grab the section of the line and modify the curve.
Can also add vertices anywhere along that line if you need to modify the curve even more. So, it behaves the same, even though the "handles" aren't there.
R_