odoo_theme/theme_clean/views/snippets_options.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <template id="clean_snippet_options" inherit_id="website.snippet_options">
        <xpath expr="//div[@data-js='Box']" position="before">
            <div data-js="gradientpicker" data-selector="section, .parallax, .s_color_blocks_2 .row > div, .s_team_profile_box">
                <we-select string="Gradients">
                    <we-button data-select-class="">None</we-button>
                    <we-divider/>
                    <we-button data-select-class="bg_gradient_primary_up"><div class="bg_option_menu_gradient bg_gradient_primary_up d-block mx-auto"/></we-button>
                    <we-button data-select-class="bg_gradient_primary_down"><div class="bg_option_menu_gradient bg_gradient_primary_down d-block mx-auto"/></we-button>
                    <we-button data-select-class="bg_gradient_white_up"><div class="bg_option_menu_gradient bg_gradient_white_up_thumb d-block mx-auto"/></we-button>
                    <we-button data-select-class="bg_gradient_white_down"><div class="bg_option_menu_gradient bg_gradient_white_down_thumb d-block mx-auto"/></we-button>
                    <we-button data-select-class="bg_gradient_black_up"><div class="bg_option_menu_gradient bg_gradient_black_up d-block mx-auto"/></we-button>
                    <we-button data-select-class="bg_gradient_black_down"><div class="bg_option_menu_gradient bg_gradient_black_down d-block mx-auto"/></we-button>
                </we-select>
            </div>
        </xpath>
    </template>
</odoo>