can't get my external harddrive to show up in bootcamp!

Can you post the output of

diskutil list

from macOS Terminal, with the G-Drive connected. If it is formatted as JHFS+, and you are on W10, the older Apple-provided JHFS+ drivers have been deprecated.

Also, see Re: Windows 10 Anniversary + Boot Camp = no longer mounting Mac partition .

Run diskpart, and post the output of

select disk 0

detail disk

list volume

Boot into macOS and post the output of

diskutil list

with the external disk connected.

See this Re: Windows 10 Anniversary + Boot Camp = no longer mounting Mac partition.

Here are the extracted steps.

Option#2, mounting via Dos Devices registry edit (ext2fsd does exactly this, this is the manual way without using ext2fsd);

Run regedit, navigate to:

HKEY_LOCAL_MACHINE/system/CurrentControlSet/Control/Session Manager/DOS Devices/

Right click-> new-> add string.

Enter drive letter you want by adding ":" to the end. In "data", type "\Device\HarddiskVolume#" where # will be your volume number of your partition as it would be detected in MS-DOS. I am sure someone would suggest a more elegant solution for this one, but you can simply navigate to Control Panel/Administrative Tools/Computer Management/Storage/Disk Management and count your partitions from beginning starting with 1. In my example, I have 1 partition on disk0, and my macOS partition is 2nd one in disk1. So my volume number # is 3.

In my registry it is "G:", "REG_SZ" and "\Device\HarddiskVolume3" for name, type, and data respectively. Your letter and numbers will be different, of course.

After making the registry tweak, cross fingers and reboot, macOS partition should be there. If something else is mounted instead, check volume number.

Restart the Windows installation and hold Alt/Option key. Do you see a selection for macOS? You can also try a NVRAM Reset.

See the link. You have to manually assign a drive letter to the external disk. Do not assign driver letter to any internal disk/partitions.

Disconnect the external drive from Windows, click on Restart in OS X, and test if you can switch to macOS.