I just got Pro version and I was disappointed you can't do this. I previously used RDPMan, which allows you to batch import a text file filled with hostnames. I can fill a folder from an export taken from AD within a minute.
Although I got fed up with rdpman, with its annoying credential error popups. So I tried this software as a colleague suggested it. I seem to prefer this interface. So I have emailed their support team explaining the feature. So we might even see them improve the "Add session" screen so that it has a batch option to repeat the import based on a CSV or text file with delimiting based on new lines or commas per host.
For me to import the servers 1 by 1, it would take so long, that the developer could implement this feature quicker than I could input them.
-EDIT- I just got a reply from the developers. It seems that in this thread the correct answer is from DiViNe. I will leave a comment to their post with additional explanation.