I installed Mojave to a MacBook Air (2015), and used bootcamp to install Windows 10 (latest SAC) as second OS followed official Apple method of BootCamp assistant.
My problem is the only possibility to select OS is the boot + option key method:
If I select Windows, the Windows version of bootcamp show only the Windows partition as boot disk, so I cannot select/boot into MacOS. Similar as on this picture: If I set the OS here, MAC will set default OS to Windows, so without holding option key, MAC will boot into Windows in the future.
If I select MacOS, the Startup Disk show only MacOS partition, so I cannot select/boot to Windows, like on this picture: If I set the OS here, MAC will set default OS to MacOS, so without holding option key, MAC will boot into MacOS in the future.
The MacBook will placed to a remote location, so I will have no access to it at boot time, cannot hold the option key.