Thank you, @mqudsi
for your helpful reply. Please allow me to rephrase that to see if I understand correctly. All of my Windows bootable drives/partitions contain an MBR (I dislike UEFI; all my boot disks are 500 GB or less), and all the other files necessary to boot Windows 10. And they are all marked "Active". Since that is the case, is my understanding summarized in my OP correct?
The reason I would like to use that feature -- if I'm right -- is when I run EasyBCD and load another partition's BCD store to make changes. I'm just a little leery of specifying drive letter "C:" as the boot drive because, while it will be assigned that letter during boot, that letter is assigned to the current boot partition rather than the target system. I'm sure I'm worried over nothing in a strictly technical sense; it's just that it makes me more comfortable to specify "BOOT" in such a case rather than "C:", even if it all ends up with the same behavior.
Given that scenario, will it cause any problems if I specify "BOOT" whenever I alter a bootable partition that's not currently running?
, I'm afraid that your reply confused me. Does it really matter what partition contains EasyBCD if I select some other partition's BCD store? I assumed that the only thing unique to the EasyBCD installation partition is that it defaults to the currently booted system's BCD store. Is that incorrect?