By title font, you mean the font used to draw the note’s title in maps and outlines? (Just checking).
Default for the whole document: set in Edit ▸ Document Settings in the Maps pane.
Change for one note: select the note, and reveal the Font panel (⌘-T)
Change for a bunch of notes: select the notes and use the font panel.
Tinderbox lets you do some elaborate things like this. For example, you might want all the notes that mention Camels to use the same map font; you’d do that with an agent. Or, you might want a note to use one font if it’s an isolated task, and a different font if it’s a project with several subtasks. For that, you’d use a rule. Or, you might want all notes that contain interview transcripts to use a special font; in that case, you’d likely have all the interview transcripts share a single prototype, and they’d inherit the font from the prototype.
Change for notes of a particular kind (e.g. Tasks): let those notes all use a common prototype. Set the font used by the prototype, and let the notes inherit the font.
Change the font in a rule or agent action: set $NameFont to the corresponding font name. For example; $NameFont=“Panton-Regular”