I want to create my site mobile first because it is where most customers view my site. Can I change the cascading rule and make mobile my primary breakpoint?
In 2023 it makes no sense to design for desktops as the primary entry point for customers.
One can design backwards from the mobile layout, to the table and through to the desktop, but designing in any direction is a choice. However, the layout you design should work on any device, monitor and browser. This is the gem of EditorX, you can do anything, including add and change breakpoints for the layout and even separate ones for independent elements on the page.
To design just for mobile would be to ignore 4/10 users on internet.
What is your goal, perhaps I am missing something?