Purchase Order > Expense Tab > Make Other Accounts Available on the List
Scenario: Accounts appearing on Purchase Order's Expense tab are only Expense Accounts.
This is because the default account for Purchase Orders is Expense Account.
To be able to see other Accounts from the list, we have to enable Accounting Preference Expand Account Lists which will allow users to have additional choices in the Account list.
Just go to Setup > Accounting > Accounting Preferences > General > General Ledger and mark the Expand Account Lists checkbox.
When this Accounting Preference Expand Account Lists is enabled, you will be allowed to select not just the Expenses but even other Accounts in your Purchase Orders such as