generate word template in custome activity

HI'

in crm 2016, i see in this link

https://community.dynamics.com/crm/b/scaleablesolutionsblog/archive/2016/07/20/auto-generate-word-template-in-dynamics-crm-2016-and-attach-in-email

option to generate word template using workflow

my problem,

I want apply it to custom entity,

and I don't see in target parameter the identity of the actiivity

it seem like some relashinship

I hope some one can help me how to fix it!!

thank's!!