There are other ways of installing Windows 10 on a external SSD, but after a lot of testing this was the most effective way that i did find for my self.
This way we can have a external SSD with Windows Boot Camp without sacrificing our internal storage, or if our internal storage is slow then this way we can get really great speeds.
One interesting thing is that on a thunderbolt unit such as the StoreJet 500 we can have besides the Windows Boot Camp Partition also a OSX installation which is great.
One downside is that we will be using a paid software but as i explain on the video is totally worth it on my opinion.
Non the less if you dont want to follow these instructions there are other ways of accomplish that shared by other users and ill share the links below. I would just like to mention that i did try those ways and i prefer the way that i show on this video specially for the simplicity, ease of use and so far i had no problems whatsoever.
This Windows 10 Boot Camp Installation on a external SSD is recorded on a Late 2013 iMac but i also made all tests successfully on my Macbook Pro Early 2015.
Hope that the video is helpful
All the Best