New “Windows Update Status Icon” added in Windows 10 April 2018 Update (version 1803) taskbar notification area or system tray if there are some notifications or alerts available from Windows Update (Settings > Update & Security > Windows Update).
The Windows Update Status Icon is containing an exclamation mark indicating a warning or alert. If you click on the Windows Update Status Icon, it opens Windows Update page in the Settings app.
“Hide for now” option in context menu (right-click menu) of Windows Update Status Icon
Step 1: Right-click on Windows Update Status Icon to open context menu.
Step 2: Click Hide for now option.
Additional note: Sometimes the Windows Update Status Icon appears again after restart or after few weeks when Windows 10 checks for newly available updates again. To completely get rid of the Windows Update Status Icon, follow the below steps to permanently disable and remove Windows Update Status Icon from Windows 10 Taskbar notification area via registry key.
Toggle off Windows Update Status Icon at Taskbar Personalization
Step 1: Go to Settings > Personalization > Taskbar at left panel.
Step 2: Click on the Select which icons appear on the taskbar link under the Notification area on the right panel.
Step 3: Toggle OFF Always show all icons in the notification area.
Step 4: Toggle OFF Windows Update Status.
Step 5: Close settings.
Registry key to permanently disable and remove Windows Update Status Icon showing in Windows 10 taskbar notification area
Step 1: Sign-in Windows 10 as a user with administrator right.
Step 2: 1. To open Registry Editor, press WIN + R keys together to launch RUN dialog box then type regedit in RUN and press Enter.
Step 3: Go to the following key:
Step 4: In right-side pane, right-click and select New -> DWORD (32-bit) Value option. Set a new DWORD name as TrayIconVisibility and keep its value as 0.
Step 5: Restart the computer to apply changes.