Numbering in Private Use Area

What is the right consistent and continous numbering (Unicode) in the Privat Use Area, starting with F000?
Is it F000 … F009, F00A … F00F, F010 … F019, F01A … F01F, F020, F021, etc.?

In the order of their values, yes. At least I cannot think of a different order that would make sense. You can add a range by choosing Glyph > Add Glyphs… and entering two Unicode names separated by a colon, e.g. F000:F0FF and Glyphs will display them for you in the right order.

Okay, thanks! The tip with the colon is very helpful!

It is a so-called ‘recipe’. More info about glyph recipes:
https://glyphsapp.com/tutorials/recipes