I’m a type designer and like to test my fonts in Affinity apps. There is one problem. If you re-install the same font with slight changes in Font Book, the systems font caches are corrupted. For me that means cleaning them and restarting every 10 minutes. Indesign (and all Adobe design apps) have the ability to load fonts from a folder in 'Application Support/Fonts' and from a 'Fonts' folder that is next to the document (the later option makes it much more convenient to work with different people on the same file). As soon as you change the font, Adobe apps will reload it and update the document.
MacOS provides great APIs to activate fonts per app so this is technically possible.