Beaver Builder Add Multiple Fonts To Plugin for Modules - https://wpbeaches.com/adding-web-fonts-beaver-builder-plugin/

enqueue.php

<?php //<~ don't add me


add_action( 'wp_enqueue_scripts', 'prefix_scripts_styles', 997 ); // All the rest load before.

function prefix_scripts_styles() {
	wp_enqueue_style( 'webfonts' , get_stylesheet_directory_uri() . '/webfonts/stylesheet.css', array() , '1.0.0', 'all' );	
}

fonts.php

<?php   //<~ don't add me

 add_filter( 'fl_builder_font_families_system', 'me_added_fonts_builder' );
 function me_added_fonts_builder( $system ) {
	 
	 $system[ 'Neutra Text Book' ] = array(
		"fallback" => "Geogia, serif",
		"weights"  => array(
			"400",
		)
	);
	$system[ 'Neutra Text Demi' ] = array(
		"fallback" => "Geogia, serif",
		"weights"  => array(
			"500",
			"600",
			"900",
		)
	);
	return $system;
 }