I'm looking to compress a set of images within Lightroom, but would like to save myself the extra step of exporting to the desktop and then reimporting into Lightroom.
You say you are going to "reimport into Lightroom," so that suggests you are going to create a web gallery within LR. If that's the case, you don't have to export and reimport. When you create a web gallery in LR, all the work is done for you. In the Web module, look at the Output Setting panel > Image Renditions > JPG Quality. That slider will determine the compression.
I apologize if I have misunderstood your question.