My PC has two hard drives.  The first "C" drive is my SSD where I keep windows, drivers & system critical stuff.  My second drive "D" is where I put everything else and where I installed ESO.  I just recently getting warnings about my "C" drive filling up.  When I looked at it, I realized that all the ESO addons were installed on there which was not what I was expecting.  I do use Minion to install my addons and they are going to the "C:/users/ME/documents/elderscrollsonline/live/AddOns" folder.  I then looked at Minion and realized that it was installing them in that "C" drive folder.  But, I have that same path on my "D" drive where my game is installed.  There were  no addons in the folder on the "D" drive.  I can tell Minion to put them there but the game is insistent on only using the "C" drive path.
I don't want to fill up my start up drive with a bunch of addons.  Why would the game be looking for addons on a different drive than what it was installed on and is there a way to get it to look on the drive where the game resides?