Trying to get more of the Tiptap buttons to work. Why does only bold, italics, strike work???

src/lib/element_tiptap_editor.svelte

@@ -1,18 +1,31 @@
 <script lang="ts">
 import { onMount, onDestroy } from 'svelte';
 import { fade } from 'svelte/transition'
-import { Color } from '@tiptap/extension-color'
-import ListItem from '@tiptap/extension-list-item'
-import TextStyle from '@tiptap/extension-text-style'
-import StarterKit from "@tiptap/starter-kit";
-import { Editor } from "@tiptap/core";
-// import Highlight from '@tiptap/extension-highlight';
+import { cubicOut } from 'svelte/easing';
 
-// import Highlight from '@tiptap/extension-highlight' ????
-// import Typography from '@tiptap/extension-typography' ????
+// Import Tiptap related modules
+import { Editor } from "@tiptap/core";
+import StarterKit from "@tiptap/starter-kit";
+import Bold from '@tiptap/extension-bold';
+import BulletList from '@tiptap/extension-bullet-list';
+import CodeBlock from '@tiptap/extension-code-block';
+import Code from '@tiptap/extension-code';
+import Color from '@tiptap/extension-color';
+import Document from '@tiptap/extension-document';
+import Heading from '@tiptap/extension-heading';
+import Highlight from '@tiptap/extension-highlight';
+import History from '@tiptap/extension-history';
+import Italic from '@tiptap/extension-italic';
+import Link from '@tiptap/extension-link';
+import ListItem from '@tiptap/extension-list-item';
+import OrderedList from '@tiptap/extension-ordered-list';
+import Paragraph from '@tiptap/extension-paragraph';
+import Strike from '@tiptap/extension-strike';
+import Text from '@tiptap/extension-text';
+import TextStyle from '@tiptap/extension-text-style';
+import Typography from '@tiptap/extension-typography';
 
 import "./element_tiptap_editor.scss";
-	import { cubicOut } from 'svelte/easing';
 
 // https://tiptap.dev/docs/examples/basics/default-text-editor
 // https://tiptap.dev/docs/examples/basics/formatting
@@ -67,14 +80,27 @@ let show_button_kv_defaults: any = {
     italic: true,
     strike: true,
     code: true,
+
     paragraph: true,
+
     heading__h1: true,
     heading__h2: true,
     heading__h3: true,
-    unsetAllMarks: true,
+    heading__h4: false,
+    heading__h5: false,
+    heading__h6: false,
+
     bulletList: true,
     orderedList: true,
+    codeBlock: false,
+    blockquote: false,
+    horizontalRule: false,
     hardBreak: true,
+
+    link: true,
+    unsetLink: true,
+
+    unsetAllMarks: true,
     undo: true,
     redo: true,
 };
@@ -93,9 +119,86 @@ onMount(() => {
     editor = new Editor({
         element: element,
         extensions: [
+            // StarterKit,
+            Bold, // part of StarterKit
+            Code, // part of StarterKit
+            CodeBlock, // part of StarterKit
+            Italic, // part of StarterKit
+            Strike, // part of StarterKit
+            BulletList, // part of StarterKit
             Color.configure({ types: [TextStyle.name, ListItem.name] }),
             TextStyle.configure({ types: [ListItem.name] }),
-            StarterKit,
+            Heading.configure({ levels: [1, 2, 3, 4, 5, 6] }),
+            Highlight,
+            History.configure({
+                depth: 100,
+                newGroupDelay: 500
+            }),
+            Link.configure({
+                openOnClick: false,
+                autolink: true,
+                defaultProtocol: 'https',
+                protocols: ['http', 'https'],
+                isAllowedUri: (url, ctx) => {
+                    try {
+                    // construct URL
+                    const parsedUrl = url.includes(':') ? new URL(url) : new URL(`${ctx.defaultProtocol}://${url}`)
+
+                    // use default validation
+                    if (!ctx.defaultValidate(parsedUrl.href)) {
+                        return false
+                    }
+
+                    // disallowed protocols
+                    const disallowedProtocols = ['ftp', 'file', 'mailto']
+                    const protocol = parsedUrl.protocol.replace(':', '')
+
+                    if (disallowedProtocols.includes(protocol)) {
+                        return false
+                    }
+
+                    // only allow protocols specified in ctx.protocols
+                    const allowedProtocols = ctx.protocols.map(p => (typeof p === 'string' ? p : p.scheme))
+
+                    if (!allowedProtocols.includes(protocol)) {
+                        return false
+                    }
+
+                    // disallowed domains
+                    const disallowedDomains = ['example-phishing.com', 'malicious-site.net']
+                    const domain = parsedUrl.hostname
+
+                    if (disallowedDomains.includes(domain)) {
+                        return false
+                    }
+
+                    // all checks have passed
+                    return true
+                    } catch (error) {
+                    return false
+                    }
+                },
+                shouldAutoLink: url => {
+                    try {
+                    // construct URL
+                    const parsedUrl = url.includes(':') ? new URL(url) : new URL(`https://${url}`)
+
+                    // only auto-link if the domain is not in the disallowed list
+                    const disallowedDomains = ['example-no-autolink.com', 'another-no-autolink.com']
+                    const domain = parsedUrl.hostname
+
+                    return !disallowedDomains.includes(domain)
+                    } catch (error) {
+                    return false
+                    }
+                    },
+            }),
+            ListItem,
+            Document,
+            OrderedList, // part of StarterKit
+            Paragraph,
+            Text,
+            Typography,
         ],
         content: html_text,
         onTransaction: () => {
@@ -399,6 +502,32 @@ let mouse_leave_wait: number = 2000;
             </span>
 
 
+            <span>
+                <!-- Links: -->
+                <button
+                    type="button"
+                    on:click={() => editor.chain().focus().toggleLink({ href: 'https://example.com' }).run()}
+                    class="btn btn-sm variant-glass-secondary hover:variant-filled-secondary rounded-md"
+                    class:variant-ghost-success={editor.isActive('link') ? 'is-active' : ''}
+                    class:hidden={!show_button_kv.link}
+                    title="Link"
+                    >
+                    <span class="fas fa-link mx-1"></span>
+                    <!-- Link -->
+                </button>
+                <button
+                    type="button"
+                    on:click={() => editor.chain().focus().unsetLink().run()}
+                    class="btn btn-sm variant-glass-secondary hover:variant-filled-warning rounded-md"
+                    class:hidden={!show_button_kv.unsetLink}
+                    title="Unset link"
+                    >
+                    <span class="fas fa-unlink mx-1"></span>
+                    <!-- Unset link -->
+                </button>
+            </span>
+
+
             <span
                 class="justify-self-end"
                 >