Custom grouping for API reference

I was advised to post my scenario here as issue:

I want different projects (and also different GIT repositories) to be merged by a so-called *CategoryAttribute*. So instead of, let's say:

```
+ A.A
- ClassT (attributed with X)
+ A.B
- ClassT (attributed with Y)
+ B.A
- ClassT (attributed with Y)
+ B.D
- ClassT (attributed with X)
```

I want a grouping like this:

```
+ X
- A.A.ClassT
- B.D.ClassT
+ Y
- A.B.ClassT
- B.A.ClassT
```

This would allow to have a set of APIs sorted by "use case" instead of real project hierarchy. Especially helpful for products that want to integrate with plugins/addins to their ecosystem.

Is that possible somehow?