Document Template update with custom fields

Hello Experts,

I have a requirement to update Document Templates in CRM WebUi. I need to add a new clause after checking a field in OpportH. Also, inside the clause, there will be custom fields from the OpportH.

Does anyone knows how can I do this?

I noticed that when I clicked the button 'Call BADI' from 'Document Template Designer',

The fields above are the available fields used inside the word template. But I cannot figure out where to add these fields mapped to OpportH.

Anyone who knows how to enhance Document Templates with custom fields?

Thanks!

Regards,

Cha