The LanguageTool desktop app for windows runs silently in the background by default, so it doesn’t appear in the taskbar unless the main window is actively open.
You can activate or open LanguageTool at any time using the shortcut Ctrl + L. Once the app is open, it will then be visible in your taskbar. If you close the window (without quitting the app completely), it will continue running in the background, but it will no longer be shown in the taskbar.
If you want to access it while it’s running in the background, you can usually find it in the system tray (the small icons near the clock in the bottom-right corner of your screen). From there, you can reopen the app or quit it completely.