You can't in the shub editor. Maybe one day that can be added but as of now. No. Also you really shouldn't write in the editor it's much better to use something like word if you have money. Or Google docs or libre office if you want something freeHello to anyone who might see this post but I'd like to ask if it is possible to increase the font size when you are using the Scribblehub editor when writing out your chapters