Descriptive Flexfield for only one template?

Summary:

Is there a way to use Expense DFF but have it display on one specific Expense Report template only?

Content (please ensure you mask any confidential information):

We are trying to find a workaround for Spend Authorization since currently it is not possible to create DFF in Spend Authorization UI. The thought is to create a new Expense Report template to be used for Spend Authorization, then adding the additional must have fields using DFFs so we can get the information needed prior to the travel.

However is it possible to add flexfields to only one specific template? When I tried adding this DFF field asking "Travel with students?", it ended up appearing on all the Expense templates, not just the new template… and that is not what we want. I would really appreciate any idea or advice!