M_DATA_MODES has two implemented modes that can also be accessed from the editor in the scene properties (static or dynamic).
Static mode pre-load all scenes data from the level, when dynamic loads only the current scene of the level, and release the memory when you change scene. "Streaming" is actually not implemented yet.

I am wondering how can I set-up a Loading-Progress-Screen,
so I am looking into the serialization code, to understand what Maratis already provide.

I found the M_DATA_MODES in MScene.h.
I think this is used to to defer the loading of the asset
of all the scenes in a level except the current one.

But surely there's more to know.
Any further information would be helpful

thanks --SIL