Hello
I hadn't seen your new question.
I made an answer on the old one
If, like me, you only have MD2, you have no choice but to tinker (I think).
EDIT a copy/paste of the answer
Hello
You just want the first level nomenclature!
The best would be to see with Dassault there is probably a module that allows you to save and modify the BOM formats (I don't have it).
Otherwise you can tinker but after generating the nomenclature you have to freeze the view containing the table.
In other words, the updates will be manual.
The trick is to import a part (not empty) which will take the number of the sub-assembly (we place it just below or above) of the sub-assembly.
We generate the numbering.
Delete under Analysis / nomenclature / definition of formats (the content of the Summary Properties window)
In CATDrawing we generate the numbers and then the table
Then in the CATProduct we delete the previously imported parts
We update the Drawing.
We remove the bubbles from the level 2 components
We replace the bubbles of the deleted pieces on the correct Level 1 Sub-Sets
The numbers of the level 1 subsets are filled in manually
We freeze the view that contains the nomenclature.
Of course, if you have to update, you will have to free the view and redo manually.
Be careful if you add parts to the option keep the existing numbering.
It's DIY.