AddRAM said:
You could not have unplugged the W10 drive if it still showing up in DM.

And lets get them drives labeled. An change the drive letter if you want to, remember you have to change the cd drive to another letter first. As I said just use Z.

Here`s an example of Disk Management from my X299 system. All my Data drives are GPT, but my W7 drive is MBR.
They're labeled correctly and hot swapping/plugging although not the best idea was only one I had left. No matter what I did, for whatever reason, and no matter what order was done in, 10 always completely destroyed win 7 boot files. Even after the hot plug 7 still showed not sign of boot files but without anything to lose I ran bcdboot from 10 no luck again but when I ran from 7 this time it worked. I went in msconfig chose settings and all good now.