How can I default expense account segment based on the expense name?

Summary:

When the user enters an expense report line and selects a particular type of expense, I need one of the segments of the expense account to default to a certain value.

Content (required):

When the user enters an expense report line and selects a particular type of expense, I need one of the segments of the expense account to default to a certain value. I wasn't able to find the expense type ('Expense Name' from the Expense Template) as an Input Source when trying to create a mapping set. Can the expense type be set up somewhere?

Version (include the version you are using, if applicable):