Do I need to know web design or coding to change the app design?

The app has a fully-featured preferences section to explore and edit behavioral options and widget design options:

Most controls are user-friendly and intuitive to use, so no coding skills are required.

In addition, if you feel confident editing CSS, it is possible to set custom styles in the 'Advanced options for' text areas for most components or use the CSS selector to move the widget to another location.