First off all, you cannot find/change the blank templates. They ALWAYS take all the properties from the Customer defaults. That is what the blank templates are designed to do.
All the other default templates you can find in the folder:
C:\Program Files\Siemens\NX 11.0\UGII\templates
But to be honest, I'm not sure which tempaltes are used for SE files. Maybe someone else here knows.
File > Open > Files of type: Solid Edge Part Files (or Solid Edge Assembly Files)
Creates NX parts on-the-fly at runtime which are populated with the data from the Solid Edge file (not a seed file). @DennisdeBrouwer is correct that the customer defaults are also read into this file - much like if you were to create a new 'blank' template.
File > Import > Part > OK > Files of type: Solid Edge Part Files
Imports the Solid Edge data into the currently displayed part file.
So to answer your question, no, Solid Edge files that are imported into NX do not use a seed file. You could create your own seed part file to be used as a template in future cases by creating a part, making whatever changes you need to define your template, and saving it with your existing templates. You could then edit your pax file to use your template on demand. You would then be able to create a new part, based on your Solid Edge template part, and import the Solid Edge part into it.
Thank you. I would like to choose the template to create these files amon other things to check calculate mass when saving for all files. Can I do that if i can use a modified template?
The problem is that I need to import a complete assembly with lots of parts and I only know how to import SE parts, not assemblies. I guess then, there is no solution for my problem.
There is an environment variable for SolidEdge sheet metal parts that changes the import behavior:
When set to 1 it will not import the flat solid body
When set to 0 it will import the flat solid body (if available).
Maybe this is useful to you.