After registering a new source system into Accounting Hub and going live for a short period, your customer identified the need to add additional transaction sources. What should you do?

There is a business requirement to display supporting information with some text and source value at the journal line level that will vary depending on the entered amounts for the line.
What is the solution to implement this requirement?

Most of the accounting entries for transaction from the source system use TRANSACTION_AMOUNT as a source of the entered amount accounting attribute. For some events, you need to use the TAX_AMOUNT source.
At what level can you override the default accounting attribute assignment?

What is the key attribute that is used to query journal entries of a registered source system?

Given the business requirement in the use case:
'New Trucks' runs a fleet of trucks in a rental business In the U.S. The majority of the trucks are owned; however, in some cases, 'New Truck' may procure other trucks by renting them from third parties to their customers. When trucks are leased, the internal source code is 'L'. When trucks are owned, the internal source code is 'O'. This identifies different accounts used for the Journal entry. Customers sign a contract to initiate the truck rental for a specified duration period. The insurance fee is included in the contract and recognized over the rental period. For maintenance of the trucks, the "New Trucks* company has a subsidiary company
'Fix Trucks' that maintains its own profit and loss entity. To track all revenue, discounts, and maintenance expenses, 'New Trucks' needs to be able to view: total maintenance fee, total outstanding receivables, rental payment discounts, and total accrued and recognized insurance fee income.
What are the key transaction types mentioned in the use case?