How to style a form item?
In each form item design form, there is a Rendering section where you can specify some CSS classes to apply. These classes can either be built-in or custom ones.
Amber front-end applications (Studio or Collect) are based on the Quasar web framework. See the “Style & Identity” section in their documentation.
A custom style can be defined in the file
src/css/custom.scss. The format of this style specification is SCSS.
See the amber-template project to integrate the custom style file into the web app built process.