@Norm With the recent option and arguably necessity to use local web fonts since GDPR I think we need a tick box option inside the Manage Fonts area that either makes fonts available or disables them inside project settings.
At first this might seem counterintuitive, but if you start adding dozens of fonts that list will suddenly become very long and most of it will be irrelevant. We need a way of managing this, so that local web fonts are quickly accessible, but not a permanent headache and I think we can take inspiration from the way a similar problem was resolved in colour management for photography.
For colour management in photography we often apply camera profiles under specific lighting conditions when processing Raw files. That’s great, but you can soon end up with a massive list of profiles that can be a pain to search through, so X-Rite created a small app called DNG Profile Manager that allows you to select or deselect what is available in compatible apps like Lightroom. Better still this can be tailored for all cameras or individual cameras. We could do something similar here so that fonts are available in all projects or just for specific ones.