I don't know why, but in my theme, customizer is hiding the options like css class for nav menu items, see the css code:

.control-section-nav_menu .field-css-classes, .control-section-nav_menu .field-description, .control-section-nav_menu .field-link-target, .control-section-nav_menu .field-title-attribute, .control-section-nav_menu .field-xfn {
    display: none;
}

The url of the script:

/wp-admin/load-styles.php?c=0&dir=ltr&load%5B%5D=dashicons,common,forms,admin-menu,dashboard,list-tables,edit,revisions,media,themes,about,nav-menus,wp-pointer,widgets,site-icon&load%5B%5D=,l10n,buttons,customize-controls,customize-widgets,customize-nav-menus,media-views,wp-color-picker,code-editor&ver=5.2.2

Also in wp-admin/nav-menus.php

<div class="menu-item-settings wp-clearfix" id="menu-item-settings-103" style="display: block;">
    <p class="field-url description description-wide">
        <label for="edit-menu-item-url-103">
            URL<br>
            <input type="text" id="edit-menu-item-url-103" class="widefat code edit-menu-item-url" name="menu-item-url[103]" value="">
        </label>
    </p>
    <p class="description description-wide">
        <label for="edit-menu-item-title-103">
            Rótulo de navegação<br>
            <input type="text" id="edit-menu-item-title-103" class="widefat edit-menu-item-title" name="menu-item-title[103]" value="Início">
        </label>
    </p>
    <p class="field-title-attribute field-attr-title description description-wide hidden-field">
        <label for="edit-menu-item-attr-title-103">
            Atributo título<br>
            <input type="text" id="edit-menu-item-attr-title-103" class="widefat edit-menu-item-attr-title" name="menu-item-attr-title[103]" value="">
        </label>
    </p>
    <p class="field-link-target description hidden-field">
        <label for="edit-menu-item-target-103">
            <input type="checkbox" id="edit-menu-item-target-103" value="_blank" name="menu-item-target[103]">
            Abrir link em nova aba
        </label>
    </p>
    <p class="field-css-classes description description-thin hidden-field">
        <label for="edit-menu-item-classes-103">
            Classes de CSS (opcional)<br>
            <input type="text" id="edit-menu-item-classes-103" class="widefat code edit-menu-item-classes" name="menu-item-classes[103]" value="">
        </label>
    </p>
    <p class="field-xfn description description-thin hidden-field">
        <label for="edit-menu-item-xfn-103">
            Relação de Links (XFN)<br>
            <input type="text" id="edit-menu-item-xfn-103" class="widefat code edit-menu-item-xfn" name="menu-item-xfn[103]" value="">
        </label>
    </p>
    <p class="field-description description description-wide hidden-field">
        <label for="edit-menu-item-description-103">
            Descrição<br>
            <textarea id="edit-menu-item-description-103" class="widefat edit-menu-item-description" rows="3" cols="20" name="menu-item-description[103]"></textarea>
            <span class="description">A descrição será exibida no menu se o tema atual suportá-lo.</span>
        </label>
    </p>
</div>

He is adding the class hidden-field to them...

Does anybody knows why is this happening?