I’ve read Glyphs Mini doesn’t have ‘Multiple Master’ font capabilities. But does it at least have the ability to create and group the four basic versions or regular, bold, italic, bold-italic into one font family group? The fontinfo screenshot shows boxes for bold/italic. But does that mean when I create those 4 versions in my application they will be nicely grouped into one font family like fonts normally do? Or will I get four separate mentions of my custom font?
Yes. style linking is supported. You just need to use the same family name in all four files.