Start with default generated template

templates/content-edit/filter-guidelines.html.twig

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+{#
+/**
+ * @file
+ * Theme override for guidelines for a text format.
+ *
+ * Available variables:
+ * - format: Contains information about the current text format, including the
+ *   following:
+ *   - name: The name of the text format, potentially unsafe and needs to be
+ *     escaped.
+ *   - format: The machine name of the text format, e.g. 'basic_html'.
+ * - attributes: HTML attributes for the containing element.
+ * - tips: Descriptions and a CSS ID in the form of 'module-name/filter-id'
+ *   (only used when 'long' is TRUE) for each filter in one or more text
+ *   formats.
+ *
+ * @see template_preprocess_filter_tips()
+ */
+#}
+{%
+  set classes = [
+    'filter-guidelines-item',
+    'filter-guidelines-' ~ format.id,
+  ]
+%}
+<div{{ attributes.addClass(classes) }}>
+  <h4 class="label">{{ format.label }}</h4>
+  {{ tips }}
+</div>