IPB/static/css/core_admin_customization_themes.css

 .ipsCms_theme_image_preview{max-height:100px;max-width:100px;}.ipsThemeKey{border-bottom:1px dotted black;}:is( #ipsTabs_tabs_form_form_tab_theme_designer_form_css_panel, #ipsTabs_tabs_form_form_tab_theme_designer_form_js_panel ) .ipsFieldRow__label{display:none;}