Scenario: A custom record sublist showing under Sales subtab on an Opportunity transaction needs to be moved under Accounting subtab of the same form. When the form is customized, there is no option to move lists between subtab.
To move custom record sublist on transaction forms, perform the following steps:
1. Navigate to Customization > Lists, Records, & Fields > Record Types.
2. Click on the custom record type name.
3. In Fields tab, click on the field name with Type=List/Record that pulls the list of Opportunity transactions.
4. In Display subtab of the field definition, set Parent Subtab to Accounting.
5. Click Save.
6. View an existing Opportunity transaction.
Actual Result: The custom record sublist should now show under Accounting tab.
Note: Unlike Entry Forms, Transaction Forms do not have an option to move sublists between subtabs by default. This is currently filed as Enhancement 191052.