New Languages

I'm in a D&D 5E campaign, but the languages are not all the same as the ones laid out in the PHB. Is there a way to add new languages?

Or a reason that adding a non-standard language to your character sheet doesn't just work? It seems odd that the drop down in the chat area doesn't auto-populate based on the lines in the Languages section of your character sheet.

You need to map a language name to a graphical font - otherwise FG won't know which font to use.

Map languages to fonts in the campaign Options window (click "Languages" at the bottom of that window). You can also enable an extension that provides extra language mappings and fonts.