How to add Custom Feed in page? The official tutorial doesnt not work

Hi,

I am following this tutorial: https://support.wix.com/en/article/displaying-different-blog-categories-on-different-site-pages But at step 4, there is no expandable arrow.

This is all I can see:

According the tutorial there should be some arrow, which after expanding should show categories of the blog posts which can be selected to be displayed. But that's not the case. There is no arrow. The feed always shows all the blog posts. ANY HELP PLEASE?

This function is the prime reason why the site will exists. There will be a lot of blog articles in different categories. And people need to see each category in each page.

Thanks for any advice.

Martin