diff --git a/src/hooks.ts b/src/hooks.ts
index 5d8b1bb..1475f91 100644
--- a/src/hooks.ts
+++ b/src/hooks.ts
@@ -1,34 +1,36 @@
 import { BasicExampleFactory, UIExampleFactory } from "./modules/examples";
-import {
-  changeProgressWindowLine,
-  isProgressWindow,
-  showProgressWindow,
-} from "./modules/progressWindow";
+import { PopupWindow } from "./modules/popup";
 import { config } from "../package.json";
 import { getString, initLocale } from "./modules/locale";
 import { registerPrefsScripts } from "./modules/preferenceScript";
 
 async function onStartup() {
+  await Promise.all([
+    Zotero.initializationPromise,
+    Zotero.unlockPromise,
+    Zotero.uiReadyPromise,
+  ]);
   initLocale();
 
-  const progWin = showProgressWindow(
-    config.addonName,
-    getString("startup.begin"),
-    "default",
-    {
-      closeTime: -1,
-    }
-  );
-  changeProgressWindowLine(progWin, { newProgress: 0 });
+  const popupWin = new PopupWindow(config.addonName, {
+    closeOnClick: true,
+    closeTime: -1,
+  })
+    .createLine({
+      text: getString("startup.begin"),
+      type: "default",
+      progress: 0,
+    })
+    .show();
 
   BasicExampleFactory.registerPrefs();
 
   BasicExampleFactory.registerNotifier();
 
   await Zotero.Promise.delay(1000);
-  changeProgressWindowLine(progWin, {
-    newProgress: 30,
-    newText: `[30%] ${getString("startup.begin")}`,
+  popupWin.changeLine({
+    progress: 30,
+    text: `[30%] ${getString("startup.begin")}`,
   });
 
   UIExampleFactory.registerStyleSheet();
@@ -50,13 +52,12 @@ async function onStartup() {
   await UIExampleFactory.registerReaderTabPanel();
 
   await Zotero.Promise.delay(1000);
-  changeProgressWindowLine(progWin, {
-    newProgress: 100,
-    newText: `[100%] ${getString("startup.finish")}`,
+
+  popupWin.changeLine({
+    progress: 100,
+    text: `[100%] ${getString("startup.finish")}`,
   });
-  if (isProgressWindow(progWin)) {
-    (progWin as _ZoteroProgressWindow).startCloseTimer(5000);
-  }
+  popupWin.startCloseTimer(5000);
 }
 
 function onShutdown(): void {
diff --git a/src/modules/examples.ts b/src/modules/examples.ts
index d5de070..a90a3be 100644
--- a/src/modules/examples.ts
+++ b/src/modules/examples.ts
@@ -1,6 +1,6 @@
 import { config } from "../../package.json";
 import { getString } from "./locale";
-import { showProgressWindow } from "./progressWindow";
+import { PopupWindow } from "./popup";
 
 function example(
   target: any,
@@ -35,7 +35,7 @@ export class BasicExampleFactory {
         ids: Array<string>,
         extraData: { [key: string]: any }
       ) => {
-        if (!addon.data.alive) {
+        if (!addon?.data.alive) {
           this.unregisterNotifier(notifierID);
           return;
         }
@@ -62,7 +62,13 @@ export class BasicExampleFactory {
 
   @example
   static exampleNotifierCallback() {
-    showProgressWindow(config.addonName, "Open Tab Detected!", "success");
+    new PopupWindow(config.addonName)
+      .createLine({
+        text: "Open Tab Detected!",
+        type: "success",
+        progress: 100,
+      })
+      .show();
   }
 
   @example
diff --git a/src/modules/popup.ts b/src/modules/popup.ts
new file mode 100644
index 0000000..ffc07c6
--- /dev/null
+++ b/src/modules/popup.ts
@@ -0,0 +1,90 @@
+import { config } from "../../package.json";
+
+const progressWindowIcon = {
+  success: "chrome://zotero/skin/tick.png",
+  fail: "chrome://zotero/skin/cross.png",
+  default: `chrome://${config.addonRef}/content/icons/favicon.png`,
+};
+
+interface LineOptions {
+  type?: keyof typeof progressWindowIcon;
+  icon?: string;
+  text?: string;
+  progress?: number;
+  idx?: number;
+}
+
+// @ts-ignore
+export class PopupWindow extends Zotero.ProgressWindow {
+  private lines: _ZoteroItemProgress[];
+  private closeTime: number | undefined;
+  private originalShow: Function;
+  public show: typeof this.showWithTimer;
+
+  constructor(
+    header: string,
+    options: {
+      window?: Window;
+      closeOnClick?: boolean;
+      closeTime?: number;
+    } = {
+      closeOnClick: true,
+      closeTime: 5000,
+    }
+  ) {
+    super(options);
+    this.lines = [];
+    this.closeTime = options.closeTime || 5000;
+    this.changeHeadline(header);
+    // @ts-ignore
+    this.originalShow = this.show;
+    this.show = this.showWithTimer;
+  }
+
+  createLine(options: LineOptions) {
+    const icon = this.getIcon(options.type, options.icon);
+    const line = new this.ItemProgress(
+      icon || "",
+      options.text || ""
+    ) as _ZoteroItemProgress;
+    if (typeof options.progress === "number") {
+      line.setProgress(options.progress);
+    }
+    this.lines.push(line);
+    return this;
+  }
+
+  changeLine(options: LineOptions) {
+    if (this.lines?.length === 0) {
+      return this;
+    }
+    const idx =
+      typeof options.idx !== "undefined" &&
+      options.idx >= 0 &&
+      options.idx < this.lines.length
+        ? options.idx
+        : 0;
+    const icon = this.getIcon(options.type, options.icon);
+    options.text && this.lines[idx].setText(options.text);
+    icon && this.lines[idx].setIcon(icon);
+    typeof options.progress === "number" &&
+      this.lines[idx].setProgress(options.progress);
+    return this;
+  }
+
+  protected showWithTimer(closeTime: number | undefined = undefined) {
+    this.originalShow();
+    typeof closeTime !== "undefined" && (this.closeTime = closeTime);
+    if (this.closeTime && this.closeTime > 0) {
+      this.startCloseTimer(this.closeTime);
+    }
+    return this;
+  }
+
+  protected getIcon(
+    type: keyof typeof progressWindowIcon | undefined,
+    defaulIcon?: string | undefined
+  ) {
+    return type ? progressWindowIcon[type] : defaulIcon;
+  }
+}
diff --git a/src/modules/progressWindow.ts b/src/modules/progressWindow.ts
deleted file mode 100644
index feabd1a..0000000
--- a/src/modules/progressWindow.ts
+++ /dev/null
@@ -1,82 +0,0 @@
-import { config } from "../../package.json";
-
-const progressWindowIcon = {
-  success: "chrome://zotero/skin/tick.png",
-  fail: "chrome://zotero/skin/cross.png",
-  default: `chrome://${config.addonRef}/content/icons/favicon.png`,
-};
-
-export function showProgressWindow(
-  header: string,
-  context: string,
-  type: "success" | "fail" | "default" = "default",
-  options: {
-    closeTime?: number;
-    backend?: "Zotero" | "system";
-  } = {
-    closeTime: 5000,
-    backend: "Zotero",
-  }
-): _ZoteroProgressWindow | Notification {
-  // Currently Zotero 7 doesn't support progress window.
-  // Use system backend on Zotero 7.
-  if (options.backend === "system" || ztoolkit.Compat.isZotero7()) {
-    Zotero.Prefs.set("alerts.useSystemBackend", true, true);
-    const notification = new (ztoolkit.Compat.getGlobal(
-      "Notification"
-    ) as typeof Notification)(header, {
-      body: context,
-      icon: progressWindowIcon[type],
-      tag: config.addonName,
-    });
-    if (options.closeTime) {
-      (ztoolkit.Compat.getGlobal("setTimeout") as typeof setTimeout)(() => {
-        notification.close();
-      }, options.closeTime);
-    }
-    return notification;
-  } else {
-    // A simple wrapper of the Zotero ProgressWindow
-    const progressWindow = new Zotero.ProgressWindow({
-      closeOnClick: true,
-    }) as _ZoteroProgressWindow;
-    progressWindow.changeHeadline(header);
-    // @ts-ignore
-    progressWindow.progress = new progressWindow.ItemProgress(
-      progressWindowIcon[type],
-      context
-    );
-    progressWindow.show();
-    if (options.closeTime) {
-      progressWindow.startCloseTimer(options.closeTime);
-    }
-    return progressWindow;
-  }
-}
-
-export function changeProgressWindowLine(
-  progressWindow: _ZoteroProgressWindow | Notification,
-  options: {
-    newText?: string;
-    newIcon?: string;
-    newProgress?: number;
-  }
-) {
-  if (!isProgressWindow(progressWindow)) {
-    return;
-  }
-  // @ts-ignore
-  const progress = progressWindow.progress as _ZoteroItemProgress;
-  if (!progress) {
-    return;
-  }
-  options.newText && progress.setText(options.newText);
-  options.newIcon && progress.setIcon(options.newIcon);
-  options.newProgress && progress.setProgress(options.newProgress);
-}
-
-export function isProgressWindow(
-  progressWindow: _ZoteroProgressWindow | Notification
-) {
-  return !(progressWindow as Notification).title;
-}