How to install Window 10 in External SSD HDD using boot camp for MacBook Pro 2017

Just got the new MacBook Pro 2017 15 and would like to install Window 10 on my External SSD HDD using Boot Camp so I can boot Window from External HDD via thunderbolt 3 port without sacrificing internal storage . There are many video tutorials to do so on YouTube. However, I could not see the option to create a Windows 10 installation drive; I'm taken directly to a screen telling me that a new Windows partition will be created.

Is it possible to install Window 10 on external drive using boot camp for new MacBook Pro 2017 ?

Thanks !