Categories and Nav sub-menus

Hello all.

I am having a great deal of trouble with 2024 WP with regards to navigation menus and categories. I was able to do this in the past but I can’t with the new block editor system. This is probably due more to my lack of understanding about the nuts and bolts of WP than the new system.

I am trying to achieve a nav bar that looks like this (items below top line are sub and subsub categories of ‘Posts’ that I would like to appear as a drop down menu):

Home Posts Etc Etc

Explore Posts by Country Explore Posts by Category

Egypt Outdoors

Turkey Food

etc etc

To create the ‘Posts’ link in the navigation menu I went to settings/reading/you home page display/posts page/posts. What I am unable to do is proceed beyond this point, and work out how to create the ‘Explore Posts by Country’ and Explore Posts by Category’ submenus. I have created them as categories, but they are ‘just names’ at this point. I don’t know how to link them to the navigation menu. I have created all the subsub categories (names of countries, names of categories) underneath the Parent Categories ‘Explore…Country’ and ‘Explore…Category’ and assigned my posts to them.

If anyone could please help I would be very grateful.

Thanks in anticipation, Jim

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