You can delete old boot menu options on Windows 10 using the BCDEdit tool. Open an elevated Command Prompt, type bcdedit /export c:\\bcdbackup, press Enter to create a backup of your BCD settings, then enter bcdedit /v to list the boot loaders currently on your system. Copy the identifier of the bootloader you want to delete, enter bcdedit /delete {identifier} replacing identifier with your own alphanumeric string, and press Enter to delete it.