Add custom font-family in tinymce email editor - sugar 12.3

I am trying to add a new Montserrat font in the tinymce editor of composer-email but without success.
Can anyone help me?

I created: source/custom/modules/Emails/clients/base/fields/htmleditable_tinymce/htmleditable_tinymce.js

({
    extendsFrom: "EmailsHtmleditable_tinymceField",

    getTinyMCEConfig: function () {
        return {
            // Location of TinyMCE script
            script_url: 'include/javascript/tinymce6/tinymce.min.js?v=' + this.tinyMCEVersion,
            // Force loading of current version of tinyMCE plugin
            cache_suffix: '?v=' + this.tinyMCEVersion,

            // General options
            theme: 'silver',
            skin: app.utils.isDarkMode() ? 'oxide-dark' : 'oxide',
            content_css: app.utils.isDarkMode() ? 'dark' : 'default',
            plugins: 'code,help,insertdatetime,table,charmap,' +
                'image,link,anchor,directionality,searchreplace,lists',
            browser_spellcheck: true,

            // User Interface options
            min_height: 250,
            menubar: false,
            statusbar: false,
            resize: false,
            toolbar_mode: 'wrap',
            toolbar: 'code | bold italic underline strikethrough | alignleft aligncenter alignright ' +
                'alignjustify | forecolor backcolor | fontfamily fontsize blocks | ' +
                'cut copy paste pastetext | search searchreplace | bullist numlist | ' +
                'outdent indent | ltr rtl | undo redo | link unlink anchor image | subscript ' +
                'superscript | charmap | table | hr removeformat | insertdatetime',
            font_formats:
                "Montserrat=Montserrat,Andale Mono=andale mono,times; Arial=arial,helvetica,sans-serif; Arial Black=arial black,avant garde; Book Antiqua=book antiqua,palatino; Comic Sans MS=comic sans ms,sans-serif; Courier New=courier new,courier; Georgia=georgia,palatino; Helvetica=helvetica; Impact=impact,chicago; Oswald=oswald; Symbol=symbol; Tahoma=tahoma,arial,helvetica,sans-serif; Terminal=terminal,monaco; Times New Roman=times new roman,times; Trebuchet MS=trebuchet ms,geneva; Verdana=verdana,geneva; Webdings=webdings; Wingdings=wingdings,zapf dingbats",
            setup: function (ed) {
                ed.contentCSS.push("https://fonts.googleapis.com/css2?family=Calibri");
                let config = App.metadata.getModule('SYNO_Settings', 'config');
                ed.on('init', function () {
                    this.getDoc().body.style.fontSize = config.email_tinymce_size;
                    this.getDoc().body.style.fontFamily = config.email_tinymce_font;
                });
            },
            // Sets the text of the Target element of the link plugin. To disable
            // this completely, set target_list: false
            link_target_list: [
                {
                    text: app.lang.getAppString('LBL_TINYMCE_TARGET_SAME'),
                    value: ''
                },
                {
                    text: app.lang.getAppString('LBL_TINYMCE_TARGET_NEW'),
                    value: '_blank'
                }
            ],

            // Output options
            entity_encoding: 'raw',

            // URL options
            relative_urls: false,
            convert_urls: false,

            // Insert image
            file_browser_callback: _.bind(this.tinyMCEFileBrowseCallback, this),

            // Allow image copy&paste
            paste_data_images: true,
            images_upload_handler: _.bind(this.tinyMCEImagePasteCallback, this)
        };
    },

})

After I create:

source/custom/Extension/modules/Emails/Ext/Vardefs/description_html.php

<?php

$dictionary['Email']['fields']['description_html']['studio']=true;
$dictionary['Email']['fields']['description_html']['tinyConfig']= [
  'theme_advanced_fonts' => "Montserrat=Montserrat,Andale Mono=andale mono,times; Arial=arial,helvetica,sans-serif; Arial Black=arial black,avant garde; Book Antiqua=book antiqua,palatino; Comic Sans MS=comic sans ms,sans-serif; Courier New=courier new,courier; Georgia=georgia,palatino; Helvetica=helvetica; Impact=impact,chicago; Oswald=oswald; Symbol=symbol; Tahoma=tahoma,arial,helvetica,sans-serif; Terminal=terminal,monaco; Times New Roman=times new roman,times; Trebuchet MS=trebuchet ms,geneva; Verdana=verdana,geneva; Webdings=webdings; Wingdings=wingdings,zapf dingbats",
];

And I created this: source/custom/include/tinyMCEDefaultConfig.php

<?php

$defaultConfig = array(

    'theme_advanced_fonts' =>  "Montserrat=Montserrat,Andale Mono=andale mono,times; Arial=arial,helvetica,sans-serif; Arial Black=arial black,avant garde; Book Antiqua=book antiqua,palatino; Comic Sans MS=comic sans ms,sans-serif; Courier New=courier new,courier; Georgia=georgia,palatino; Helvetica=helvetica; Impact=impact,chicago; Oswald=oswald; Symbol=symbol; Tahoma=tahoma,arial,helvetica,sans-serif; Terminal=terminal,monaco; Times New Roman=times new roman,times; Trebuchet MS=trebuchet ms,geneva; Verdana=verdana,geneva; Webdings=webdings; Wingdings=wingdings,zapf dingbats",

);

And nothing happens.

Does anyone know how to add a font in a sugar 12.3 version?

Kind regards,