I would think that reducing canned beef broth enough that it "thickens" in consistency would result in it being VERY salty!
Am not sure what you are trying to accomplish by reducing it.
I looked up a couple of German meatball recipes and found beef broth, lemon juice and capers to be common ingredients. Also some use sour cream.
None reduced the broth. They either used a roux or deglazed the meatball cooking pan and added flour, then the capers and lemon juice or sour cream.
Less is not more. More is more and more is fabulous.