x64 It seems to me that the gray button BM only in x64 (Win8.1, Win7 and WinPE 5.0). Because it has been available in my Windows To Go x86. But in Windows To Go x86 is not install correctly PHDM14S (ie install but then did not work, and repair does not help), but there works in PHDM14Pro
No UEFI, MBR From x86 I can install / edit BM on any internal or external drives (except GPT) From x64 - no matter what, the button is not active at all.
I tried again on a clean Windows To Go x86 install PHDM14S. Now all works including BM. Strangely. Unlike the previous one, I did not install the Hot Core driver and there wasn't installed PartitionGuru program (which usually have all my OS) Maybe they conflict? ------------------------ It seems that after all the reason in the OS bit. Third-party software is not to blame.