I'm afraid it's not possible to embed Segment or Splines in macros.
These are special objects, linked with the Max parameters, where we store a reference to the object, scene node, material and more.
Instead macros (really the full style) are handled as text (in XML format). That lets us to copy/export/import macros easily. There is no a simple way to embed a Max object in that format.
Also there are other reasons to keep these special objects in the main style only.
I love the new random option resetting on different states but I`m still not sure about the hierarchy of Generators. On what level of Generator restart applied when nesting?
Interesting question. Everything works by events: when a generator is going to be evaluated, a 'Generator' event is triggered, and propagated to all child nodes.
When Random node receives this event, its internal random generator is reset.
In case of nested generators, there are multiple events. For example, with 'Random->Gen1->Gen2':
1. A 'Generator' event is sent at start of Gen2 evaluation.
2. Since Gen2 uses Gen1, Gen1 is evaluated, triggering other 'Generator' event.
If Gen1 is used multiple times by Gen2 (for example, when connected to 'Default'), Gen1 is evaluated multiple times, triggering its own 'Generator' for each iteration.