You will only do this if you already go to the Taskbar Settings and check that the Power icon is set to ON and not OFF. But for the Bluetooth icon, there's no such thing inside the Taskbar Settings. Only the clock, volume, network, power, input indicator, location, action center, touch keyboard, Windows ink workspace, and touchpad are available there.
How to restore a missing battery, Bluetooth, and other system tray icons in Windows 10.
1. Right-click your Taskbar and press Task Manager.
2. Under the Windows Processes, find Windows Explorer. Right-click on it, and then press End task.
3. Your screen will turn black but don't worry. Press File > Run new task.
4. Inside Create new task, type explorer.exe, and press the OK button.
5. And there you have it. Recheck your system tray for the power or Bluetooth icon which was missing, if the icons are there now.
If this tutorial did not work, then try restarting your PC. And if restarting your PC did not also work, then try scanning your PC for file errors. See tutorial below:
1. Scan your PC or laptop computer for file errors or corrupted files.
2. Go to Start > type cmd and press Enter. Run Command as Administrator.
3. Inside cmd, type sfc /scannow and hit Enter.
4. Just wait for some time until scanning finishes.
Lastly, maybe Bluetooth is not enabled in the Notification (Action Center).
1. Just click the Notification icon near your computer (system) time.
2. A menu will appear. Find the Bluetooth icon there and click it.
3. The icon will then appear in your taskbar or system tray.