Q: Mac formatted Hard drive does not show up in bootcamp Windows 10

Please connect the WD HD to the OSX side and post the output of the OSX Terminal command

diskutil list

Windows 10 has broken the HFS+ driver that Bootcamp drivers package installs to allow read-only access to Apple HFS+ partition. Please see Re: Windows 10 Anniversary + Boot Camp = no longer mounting Mac partition .

Your Seagate drive is Apple HFS. If you need to see this disk, then, in OS X, shrink the 2TB partition by some amount of space, and format the newly freed-up space as FAT32. Windows 10 will be able to read-write as well as OS X. All your flash drives are usually FAT32.