If I start the configuration window (BTT preferences) from the right-side status menu bar, all the left-side menu bar items are available. If I start the configuration window by clicking the BTT icon in the dock or the launchpad, while BTT is already running (indicated by the status icon), then the left-side menu bar items are not accessible at all.
This is a bug that I can live with but quite annoying. BTT occasionally crashes when I test new configurations so it is convenient to restart by clicking the BTT icon residing in the dock, but I would inevitably click on such an icon to open a configuration window, leading to a half-functioning configuration window. In fact, BTT is the only app that exhibits this odd behavior so I cannot really remember to avoid clicking on the dock icon.
I am using a 2018 MBP 15in, Catalina 10.15.6, BTT 3.402. I have had this problem since I started using BTT on July 31.