Create Shortcuts in MuseScore 4 Studio

In Musescore 3, I had created keyboard shortcuts, for instance to join beams in a measure. I seem to have forgotten how to do that. In MuseScore 4 Studio, I selected Preferences and located the "join beam" icon and assigned (on a Mac) command-control-B. the program apparently accepted that, but when I attempt to use it, nothing happens.