Bernard,
I can share one of our methods to create BOMs. Maybe you will be interested.
In some cases, the engineer creates the BOM in a spreadsheet format. I have utilized the "Import from Spreadsheet" functionality to import the Excel BOM into Windchill. You just need to have it in the right format for the import engine. I can provide more details if you wish.
To answer your original question... Yes, there is still a Product Structure Explorer in Windchill 10.2. What version of Windchill are you currently using?