How do I change the default font and size for my Todoist lists?
unfortunately, it's not possible to change the font size in Todoist. You could use external browser plugins which could change the font on any website or simply use the Ctrl+ and Ctrl- (that's Control and plus or minus) shortcuts to zoom in the page.
Ctrl + didn't work.
Do you have a scroll-wheel on your mouse. This could also work, please press Ctrl and up or down on your mouse scroll wheel.