diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index 4f145c494973374e87f3a3ed5eb6b33a43c518c8..3b588199c8ab98157cc423e47fa209d7899d8656 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -13,6 +13,15 @@ ChromeUtils.importESModule("resource://gre/modules/NotificationDB.sys.mjs");
 
 // lazy module getters
 
+const ZEN_WELCOME_PATH = "zen-welcome";
+const ZEN_WELCOME_ELEMENT_ATTR = "zen-dialog-welcome-element";
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "ProfileService",
+  "@mozilla.org/toolkit/profile-service;1",
+  "nsIToolkitProfileService"
+);
+
 ChromeUtils.defineESModuleGetters(this, {
   AMTelemetry: "resource://gre/modules/AddonManager.sys.mjs",
   AboutNewTab: "resource:///modules/AboutNewTab.sys.mjs",
@@ -1610,6 +1619,7 @@ var gBrowserInit = {
     // Update the chromemargin attribute so the window can be sized correctly.
     window.TabBarVisibility.update();
     TabsInTitlebar.init();
+    ZenThemeHandler.init();
 
     new LightweightThemeConsumer(document);
 
@@ -1735,6 +1745,11 @@ var gBrowserInit = {
     }
 
     // Misc. inits.
+
+    // ZEN: Propagate the current profile used to the browser UI, such as 
+    // showing the avatar and profile info to the side bar
+    zenUpdateBrowserProfiles();
+    
     gUIDensity.init();
     TabletModeUpdater.init();
     CombinedStopReload.ensureInitialized();
@@ -2489,6 +2504,7 @@ var gBrowserInit = {
     TabsInTitlebar.uninit();
 
     ToolbarIconColor.uninit();
+    ZenThemeHandler.uninit();
 
     // In certain scenarios it's possible for unload to be fired before onload,
     // (e.g. if the window is being closed after browser.js loads but before the
@@ -6660,7 +6676,7 @@ function setToolbarVisibility(
       );
     }
 
-    const overlapAttr = "BookmarksToolbarOverlapsBrowser";
+    const overlapAttr = "BookmarksToolbarOverlapsBrowser__ignore"; // Original string was "BookmarksToolbarOverlapsBrowser" but it's not used and it only bugs the UI.
     switch (isVisible) {
       case true:
       case "always":
@@ -9780,6 +9796,13 @@ var gDialogBox = {
     parentElement.style.removeProperty("width");
     parentElement.style.removeProperty("height");
     document.documentElement.setAttribute("window-modal-open", true);
+
+    if (uri.includes(ZEN_WELCOME_PATH)) {
+      parentElement.setAttribute(ZEN_WELCOME_ELEMENT_ATTR, true);
+    } else if (parentElement.hasAttribute(ZEN_WELCOME_ELEMENT_ATTR)) {
+      parentElement.removeAttribute(ZEN_WELCOME_ELEMENT_ATTR);
+    }
+
     // Call this first so the contents show up and get layout, which is
     // required for SubDialog to work.
     parentElement.showModal();
@@ -10157,3 +10180,45 @@ var FirefoxViewHandler = {
     this.button?.toggleAttribute("attention", shouldShow);
   },
 };
+
+function zenUpdateBrowserProfiles() {
+  const mainWindowEl = document.documentElement;
+  // Dont override the sync avatar if it's already set
+  if (mainWindowEl.style.hasOwnProperty("--avatar-image-url")) {
+    return;
+  }
+  let profile = ProfileService.currentProfile;
+  if (!profile || profile.zenAvatarPath == "") return;
+  // TODO: actually use profile data to generate the avatar, instead of just using the name
+  mainWindowEl.style.setProperty("--avatar-image-url", `url(${profile.zenAvatarPath})`);
+} 
+
+var ZenThemeHandler = {
+  init() {
+    window.addEventListener("windowlwthemeupdate", this);
+    window.addEventListener("nativethemechange", this);
+    this.executeAllUpdates();
+  },
+
+  uninit() {
+    window.removeEventListener("windowlwthemeupdate", this);
+    window.removeEventListener("nativethemechange", this);
+  },
+
+  handleEvent(event) {
+    this.executeAllUpdates();
+  },
+
+  executeAllUpdates() {
+    this.updateAccentColorPref();
+  },
+
+  updateAccentColorPref() {
+    let root = document.documentElement;
+    const themeAccent = Services.prefs.getStringPref(
+      "zen.theme.accent-color",
+      "#0b57d0"
+    );
+    root.style.setProperty("--zen-primary-color", themeAccent);
+  },
+}