Add an Add-ons shortcut in about:preferences

application/basilisk/components/preferences/in-content/preferences.js

@@ -193,6 +193,18 @@ function helpButtonCommand() {
   openHelpLink(helpTopic);
 }
 
+function openAddonsSidebarLink(event) {
+  event.preventDefault();
+  event.stopPropagation();
+
+  if (window.top && typeof window.top.BrowserOpenAddonsMgr == "function") {
+    window.top.BrowserOpenAddonsMgr();
+    return;
+  }
+
+  openUILinkIn("about:addons", "tab");
+}
+
 function friendlyPrefCategoryNameToInternalName(aName) {
   if (aName.startsWith("pane"))
     return aName;

application/basilisk/components/preferences/in-content/preferences.xul

@@ -87,7 +87,8 @@
   <hbox flex="1">
 
     <!-- category list -->
-    <richlistbox id="categories">
+    <vbox id="preferences-sidebar">
+    <richlistbox id="categories" flex="1">
       <richlistitem id="category-general"
                     class="category"
                     value="paneGeneral"
@@ -176,6 +177,13 @@
         <label class="category-name" flex="1">&paneAdvanced.title;</label>
       </richlistitem>
     </richlistbox>
+    <hbox id="preferences-sidebar-footer" align="center">
+      <label id="sidebar-open-addons"
+             class="text-link"
+             value="&openAddonsSidebar.label;"
+             onclick="openAddonsSidebarLink(event);"/>
+    </hbox>
+    </vbox>
 
     <keyset>
       <!-- Disable the findbar because it doesn't work properly.

application/basilisk/locales/en-US/chrome/browser/preferences/preferences.dtd

@@ -21,6 +21,7 @@
 <!ENTITY  paneContainers.title    "Container Tabs">
 <!ENTITY  paneSecurity.title      "Security">
 <!ENTITY  paneAdvanced.title      "Advanced">
+<!ENTITY  openAddonsSidebar.label "Add-ons">
 
 <!-- LOCALIZATION NOTE (paneSync.title): This should match syncBrand.shortName.label in ../syncBrand.dtd -->
 <!ENTITY  paneSync.title          "Sync">

application/basilisk/themes/shared/incontentprefs/preferences.inc.css

@@ -45,14 +45,26 @@ treecol {
 
 /* Category List */
 
-#categories {
+#preferences-sidebar {
   max-height: 100vh;
 }
 
+#categories {
+  max-height: none;
+}
+
 #categories > scrollbox {
   overflow-x: hidden !important;
 }
 
+#preferences-sidebar-footer {
+  padding: 8px 15px 12px;
+}
+
+#sidebar-open-addons {
+  margin: 0;
+}
+
 /**
  * We want the last category to always have non-0 getBoundingClientRect().bottom
  * so we can use the value to figure out the max-height of the list in