If the signature always follows with the cursor, every time you click the mouse, it will add a new signature, then how can you click it off?
Maybe there is some room to play around with the UX, but unfortunately, we don’t support this at the moment.
However, there are two alternatives may help you:
If you select a signature annotation, and hold your alt key to drag and drop, it will copy the current annotation;
You can also select an annotation, and then use ctrl+c and ctrl+v to copy/paste annotations
Both ways will give you some convenience to duplicate the current annotation, I hope these may help!