Dual Boot Default OS Change

That's an W7 factory install on a Dell. I haven't moved, marked or repaired anything after adding the second HD and installing W10. IIRC, on 9860 build, W10 as default OS, I could reboot into W7 but could no longer do that on 9879 but put W7. Maybe an update changed that.

Having W7 as the default is no problem, it doesn't matter as long as I have a path to change. My question was, how to change the default OS from the command prompt? One solution from my TechNet post was to use BCDEDIT /Default (boot loader identifier) which should work.

I've just looked at from what 10 wants to be stand point,
10 wants to be the default and changes to that goal every shut down or boot for updates,
What I've done is added a hot swap ssd case,
Only one ssd is ever inserted or hot at any one time so each boot loader is independent of each other and works best that way,
If I want to use 7 I insert that ssd and 10 the same no possible corruption from 10 to 7's booting
Alpha 10 will not frustrate me anymore on startup or complete removal of 10 to clean install anther build if I feel the need too