As a follow-up, running dnfdragora with the Qt toolkit doesn’t have the window height problem–it works much better. To use the Qt toolkit, all that I needed to do was:
sudo dnf install libyui-qt
and then I was able to run dnfdragora --qt . The full window is visible on the small screen, giving you access the essential buttons at the bottom of the window.
Another workaround mentioned in response to my comment on the GitHub bug report above was they were able to increase the scale in the Xfce display settings to temporarily make the screen resolution larger. I tried that and it does work with the Gtk version of dnfdragora, though, I think using the Qt version is nicer for now.