When Opera is open, you can goto the URL opera://about and look at the "install" path to find launcher.exe. You can then browser to the install folder in Windows Explorer (File Explorer) (with file extensions and hidden items turned on under view -> show), right-click launcher.exe and choose to create a shortcut for it. You can then cut and paste that shortcut to your desktop. You can also right-click launcher.exe and choose to pin it to the start menu. You can then right-click launcher.exe and pin it to the taskbar.
Also, when Opera is running, you can right-click on its taskbar button and choose to pin it to the taskbar if you like doing it that way instead.
If you hit Windows key + r to open the run dialog, type:
explorer "%LOCALAPPDATA%\Programs\Opera GX"and press enter, that should open the Opera GX install folder for you.
If that doesn't work, you can try:
explorer "%ProgramFiles%\Opera GX"instead. Or, just look at the "install" path shown at opera://about as mentioned earlier.
Now, if you uninstall (don't choose to delete your data when uninstalling), delete the install folder if it remains, and reinstall, Opera should show back up for you.