@Jmandyass, Manager does not function the way you describe. So you cannot do what you did at your prior law firm. A customer is a customer, and is already a subsidiary ledger of the Accounts receivable control account. The customer cannot have subsidiary matters or records underneath.
Tracking codes will not work for this purpose. They were originally designed to separate income and expenses for divisions of a business. While you could assign tracking codes for each new matter for every client, those tracking codes would not be related to the client in any way within the program. They would be better for tracking, as an example, how much income you made overall from settling estates or your net profitability from your divorce practice.
One feature of Manager that might be useful is to make extensive use of Billable Time. Read the Guides about recording and invoicing billable time. Adding custom fields to your billable time entries would allow you to designate which matter a particular entry applied to. But that will be information only.
Understand that Manager is an accounting system, recording financial transactions. It is not intended as, and does not perform, the functions of an integrated practice management system like you describe. It would not allow you to link one matter to another or keep records and manage documents related to a matter as specialized software for legal practices often does. Sure, you could use some of Manager’s features to crudely approximate some of those functions. But you might never be satisfied.
That said, Manager can certainly handle accounting for a legal practice. First, you need to determine what your requirements are. Then, you need to decide what accounting functionality is needed to satisfy them. You might need to consult an accountant at this stage. Only then will you be able to figure out whether Manager will satisfy your needs.