@chipf0rk: There's a button to show the current font the alias points to, as well as one to reset it to the defaults.
Each of the four base families can be overriden (serif: Caecilia Regular, sans: Helvetica, mono: KindleSymbol, condensed: Caecilia Condensed), but since I don't care about condensed, and I don't recommend overriding a font used it the UI (ie. sans/serif/mono), I went with condensed.
So, yeah, while you *could* override more than one family, I don't really recommend it
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You'll have to restart the framework (there's a button for that in the Fonts menu) for the changes to be taken into account (or update the cache if it's the first time the fonts have been introduced, in which case the framework restart is part of the process).
I'll probably tweak the doc a bit when I make the proper release, so don't hesitate to ask, it'll help me make it clearer for everybody else
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