How to transform 3 and more level folder structures after migrating to version 4?

Question

There are often used 3 and more level folder structures in versions before 4.0. This is the simplest one:

1. Customer
2. Project 
3. Document

According to Folder Structure approach it is not possible to build such structures. The problem is that 2nd level in this case is Product / Project folder that holds a lot of information about the project itself and it is not convenient to move all Project fields to Document form. Nobody will fill >10 additional fields for each document every single time. 

Question: how to solve such cases in version 4?

Answer 1

The idea is to create two different object type groups. One for customer management and one for project management.
Each of these groups has a single folder type aka „context folder" - in your use case "customer" and "projects". If you want to create relations between customer folders and project folders, you can use reference fields. The main advantage of this concept is that there is no single truth - no hard-coded hierarchy. One customer can refer to many projects and one project can refer to many customers.
The references are resolved in real time and can be seen under the aspect "References" in the object detail view. In future versions, you can also use references in the structure service.