process Field name for message template in onboarding

Content

I am searchng for a way to know the field name I can use in a message tamplate.  When I create one in onboarding it only gives me the limited choices such as newhirepersonalinfo fields.  However we have built other fields but I don't know how my former coworker knew what syntax to use.  The one I need specifically is the field name of the onboarding process chosen. this process version is chosen at the start of onboarding and displays as a column in our onboarding.  For example ours say external or internal onboarding to differentiate between type of hire/transfer.