mkdocs-site/hooks/nav.py

import jinja2

def is_list_page(page) -> bool:
    if not page.parent:
        return False

    return page.parent.children[0] == page

def children(page):
    if not is_list_page(page):
        return []
    return page.parent.children[1:]

@jinja2.pass_context
def get_page(context, slug):
    nav = context["nav"]
    for page in nav.pages:
        if page.file.src_uri == slug:
            return page
    return None

def on_env(env, config, files):
    env.filters["is_list_page"] = is_list_page
    env.filters["children"] = children
    env.globals["get_page"] = get_page