Woocommerce: The predefined attribute selection is absent

Hi everybody!

I’d like to add the predefined product attribute in Woocommerce, i.e. the attribute which type is “Select”.

But unfortunately the appropriate select switch is absent on this page.

This is the screenshot.
https://prntscr.com/pyrpsr

I have following software versions:

WordPress – Version 5.2.4
Woocomerce – Version 3.8.0

BTW the predefined attributes are exist in my product database. But this attrivutes are in the demo content I’ve downloaded from supplier.

Please help!

The page I need help with: [log in to see the link]