The link associated with Use and customize form templates is incorrect. 

https://quickbooks.intuit.com/learn-support/en-ca/sales-customers/how-to-customize-and-manage-paymen...

The correct link is

https://quickbooks.intuit.com/learn-support/en-ca/getting-started/use-and-customize-form-templates/0...

I second the suggestion.  I want to associate Payment Terms to an Invoice Template.   At a minimum adding the Terms for the Company would solve all the unpopulated (500 plus) customers I have.

Taking this one step further, I should be able to set a default Payment Term for the Company in Preferences, then if configured for the Invoice type and then finally the Client info itself.