In my videos I have some information at the end of the video that occupies the whole page. There are annotations that could be scaled to fit but that's too many steps and I have to drag the corners so the annotation is 100% of the viewing surface. This is time consuming
I agree with @Dubie, saving to the Library is a great idea.
With reference to 'scaling to fit' are you using the context menu (right click) and scaling to fit? It depends on the annotation and the canvas dimensions you're using, but this could be an alternative quicker way than dragging the corners.