If you want to assign a VST3 category - e.g. ‘Analyzer’ - to the AudioPluginDemo in the Projucer, it appears straight forward to click the ‘Analyzer’ checkbox. But instead of changing the category, it makes the AudioPluginDemo disappear in Cubase 9.5 (macOS).
Turns out that besides the chosen category, ‘Fx’ or ‘Instrument’ must be selected as well in order to make Cubase 9.5 recognize the plugin. This is not required by other hosts.
It would be very helpful if the Projucer would make it impossible to leave ‘Fx’ && ‘Instrument’ unchecked in the ‘Plugin VST3 Category’ list. Or at least mention this in the info/help bubble.