Review the ‘WordPress Theme Hierarchy’ document here: https://developer.wordpress.org/themes/basics/template-hierarchy/ It explains how templates are selected according to function and availability. The chart is helpful.
How to create a template for a post in Query Loop block?
WordPress theme.json: Why doesn’t “contentSize” work
WP Update Messages get cut off during Theme update
Looks like it can be fairly trivially achieved with a hierarchical custom post type and a menu widget in the sidebar. Menus come with current page CSS classes out of the box that can be styled as you require.
Your query there is looking for results from either post type that have the meta value. AFAIK there’s no way to do that in a single query unless you also add the checkbox to the other post type.
try using the updraft backup plugin to take a backup of your modified theme and restore it to another website.
How to enable wc_add_to_cart_message?
Adding features to Gutenberg without theme.json
I want to move the one click accesbility button on bottom of my website screen,