To open the code editor - click on the Code tab.
Every operation that you might perform within the visual builder or by the left inspectors is generating clean, battle-tested code.
Using Code Editor you can edit and integrate the webpages all the time: add custom .css rules or modify elements' classes is matter of seconds, and the effects are displayed in real time in the canvas. Above all you can even create multiple js files and integrate them with your HTML.
Note: When you open CSS / JS / JSON files, it will directly open the code editor
Code Editor Toolbar
If you want preview the changes as you code, you can always use the toggle split preview button from the top right in the Code Editor Toolbar to open the Preview screen in the split mode.
If you would like to use SVG icons from the code editor, from the top left in the code editor toolbar click on leaf icon, this will open the SVG icons gallery. Nearly 300+ SVG icons are available for use, you can even search them and use it in your projects.