I was looking for how to limit the number of links listed too. It is such a common feature in widgets I’m surprised it isn’t included.
When using the shortcode on a page I would not be likely to want to limit the number of links. However, in the sidebar a long list would not be useful and I would likely only want 3-5 to be highlighted there.
Specific case: I’m using it to list articles in the press about our nonprofit. I have a page that displays all of the links. I also feature them in the sidebar. However, we’ve now reached the point where the number of articles is taking up too much space in the sidebar. My workaround will have to be to create two categories, one specifically for the sidebar. This will require more oversight from me. As the links age, I will have to remove them from the category I’m using for the sidebar. Being able to limit the number of links showing in the sidebar would handle this automatically.