I’m not sure if this has been discussed already, but I found another issue with the Bootcamp utility in the latest version of Mojave. As we know already, the Bootcamp utility has been non-functional on Mojave running on the MacPro5,1, but in the past I’ve been able to run it on another compatible machine, then use the USB stick installer on my Mac Pro to install Windows. That appears to be no longer the case. The first issue (under Mojave 10.14.3 and the October 2018 Windows ISO) was an error about not enough space on the USB stick, which seems related to this article here: https://support.apple.com/en-us/HT209351. After updating to Mojave 10.14.4 as the article directs, the Bootcamp utility succeeded in making a USB stick installer. However, the MacPro5,1 appears to be unable to see this USB stick in the boot menu nor in the Startup Disk control panel (other machines can see and boot from it, however). From my investigation so far, it appears that the new Bootcamp utility now formats the USB stick installer as ExFAT rather than FAT32, which I believe is not supported for booting on the MacPro5,1. What I discovered when I tried to work around this with Unetbootin, is that the Windows installer file “install.wim” exceeds 4GB in size, which means it exceeds the maximum file size of the FAT32 partition format. So it appears that a Windows installer cannot be put on a FAT32-formatted USB stick anymore. There are older versions of Windows with “install.wim” files under the 4GB limit, but I’m not sure how far back you have to go (even the April 2018 version exceeds it, which seems to be the latest version you can download from Microsoft). Regardless of which version of Windows you use, the Bootcamp utility now appears to only use ExFAT when formatting the drive. So it appears that your options now are: 1) use an older windows installer ISO with an older version of Bootcamp on another machine to create the installer, or 2) burn the ISO to a DVD and boot from that. I was not able to find any other workarounds so far. Hope this helps someone.