With few exceptions, objects are created on the current work layer. You will need to change the work layer before creating the object, or move the objects to the desired layers after creation. I know of no "out-of-the-box" method to automatically create/move a certain object type to a designated layer.
The only 2 ways I can think of....
1) Before creation
Use Menuscript to add /PRE actions (to all object types you care about) to set the work layer "appropriately". If you want to use ranges (e.g. all datums on layers 20-25) you could check the current layer is in that range, and if not, you'll have to figure out a rule as to which layer to use.
2) As a "cleanup" action
(possibly as a Manuscript "/PRE" action on all the "Save" options?) Examine all geometry, move to appropriate layer as needed.
Production: NX10.0.3.5 MP16/TC11.2
I'd rather be e-steamed than e-diseaseled