For many of the places text is displayed (conversations, plaques, item descriptions, etc.), basically anything that asks for text in the editor, you can use HTML codes to specify any kind of text font or size you want. For the system stuff, you can make changes to the app itself, or have a programmer do it for you.
One place I am running into trouble is the tabs section. If I try to add styling to the text boxes for my menu tabs in appears to work in the editor but in the game it breaks and displays the code instead. Is there a way around this. We would really like to make the menu look more customized.
The titles of the tabs, along with the titles of most things like plaques, are not stylable. I do think it would look cool if they were, but I bet also rather messy in the details as the existing space for the the titles would need to reflow along with different size text.