Embed query to list children notes

There is a plugin/widget combination already:

• HierarchyNavigate + listChildDocs

In the settings of HierarchyNavigate you can change the page layout to include the listChildDoc widget which will then be inserted automatically.

Bro, I think you should definitely take a look at the plugin in the link below, it looks like it does exactly what your screenshot shows it does
https://github.com/TinkMingKing/siyuan-plugins-index

Is it like this plugin to display the upper and lower documents? https://github.com/OpaqueGlass/syplugin-my-plugin-collection/blob/main Or do you want to implement other styles, I'm not quite sure what you mean

Please check provided screenshot, it is Outline product. Maybe this is possible in SiYuan?