An example of how to add custom fonts to Getwid Blocks.

getwid-add-custom-fonts.js

// hook allows to disable Google Fonts
wp.hooks.addFilter('getwid.fontsControl.enableGoogleFonts', 'getwid', function (enabled) {
    // current Google Fonts status(load or not) is passed to function as parameter
    // should return true or false
    // if return false - Google Fonts won't be loaded
    return enabled;
});    

// hook allows to filter lists of fonts and add custom
wp.hooks.addFilter('getwid.fontsControl.fonts', 'getwid', function (fonts) {
    // list of fonts passed to function as parameter
    //
    fonts.push({
        id: 'my-test-font-group',           // - string, identifier of fonts group, can't be empty string '' or 'google-fonts'
        title: 'My Test Font Group',        // - string, name of fonts group
        items: [                            // - array of font objects
            {
                title: 'Font Title 1',      // - string, font title displayed in control
                family: 'My Test Font 1',   // - string, font-family name
                variants: [                 // - array of available font weights
                    '100',
                    '200',
                    '300',
                    '400',
                    '500',
                    '600',
                    '700',
                    '800',
                    '900',
                ]
            },
            {
                title: 'Font Title 2',
                family: 'My Test Font 2',
                variants: [
                    '300',
                    '400',
                    '500',
                    '700'
                ]
            }
        ]
    });
  
    // should return array of objects with some required properties, example above    
    return fonts;
});

getwid-enqueue-custom-font-script.php

add_action( 'enqueue_block_editor_assets', function (){ // js script should be enqueued only for editor
	wp_enqueue_script(
		'my-test',
		PATH_TO_YOUR_FILE . '/js/getwid-add-custom-font.js',
		[
			'wp-hooks' // js script should have wp-hooks in dependencies
		]
	);
} );