Is there a quick way to disconnect all objects from a merge from scene null model, but not loose, parents /constraints that are associated which the objects within the model.scene.null ?

The only way I currently know of is to manually go into the schematic view and disconnect each object from the null, I hope there is a faster alternative.

Cutting Links in a Hierarchy
You will often need to cut the hierarchical links between a parent and its child or children in a hierarchy of objects. If the child is also a parent, the links to its own children are not affected.

A cut object becomes a child of its model. If an object is cut from its model, it becomes a child of the parent model.

To cut an object from its parent
1. Select the object you want to detach from its parent.
2. Do one of the following:
- Click the Cut button in the Constrain panel.
or
- Press Ctrl+/
or
- In the explorer, drag and drop the child to another node

You should be able to detach several objects at once. Just open the explorer or schematic for the merged root, select the parent nodes you want detached, and hit cut or ctrl+/.  It should remove them to the scene root with their children in tact.