I use Fancy Product Designer (HTML5 Product Designer for Wordpress and WooCommerce. Create and sell customizable products) Version 3.3.1 | By Rafael Dery | radykal.de.
When active plugin and go to "Customize" it view number 2 (file att "khac-nhau.png").
How to config, set... view Customize = number 3.
Sorry I'm not sure I understand you correctly. You want to increase the width of the designer on your page? That can be done with some custom CSS (added via the UI & Layout Composer) and possibly some settings (both of these depend on your theme so there is no general solution - please open a support ticket if you need help).