Gatsby - create index.js in every subdirectory - reactjs

Question

My Gatsby site sources its content from YAML files rather than Markdown. There are a bunch of categories and subcategories, such that valid paths are like:
mysite.com/movies/drama/war/1980s
mysite.com/video-games/puzzles
etc...
I would like to create an index.js for every subdirectory: /movies , /movies/drama, /movies/drama/war, /video-games, etc.
My strategy is to get a list of all the pages, from which I can extract all the unique paths and createPage an index.js in each. However I tried querying
{
allSitePage {
nodes {
path
}
}
}
during gatsby-node's createPages but none of the paths had been created yet -- only the root and 404 paths existed (probably because these are the only files in my /pages directory?)
I'm guessing there's a better way to do this anyway. How can I create an index.js in every subdirectory? Thank you.
EDIT: I realized createPage is an asyncronous function, my query was running before the createPages had completed. I adjusted all my code with async/await to ensure the pages were created prior to running the allSitePage query -- but it still comes up empty. Now really confused. (Another note: in the GraphiQL browser, the query of course shows all the pages. They just don't seem to be available until after gatsby-node.js completes)
2nd EDIT: I was asked to post my createPage() code:
const postsYaml = resultYaml.data.allYaml.edges
// 1-1 mapping between YAML edge and Gatsby page
// use Promise.all() to ensure all pages are created before continuing
await Promise.all(postsYaml.map(async (post, index) => {
const previous = index === postsYaml.length - 1 ? null : postsYaml[index + 1].node
const next = index === 0 ? null : postsYaml[index - 1].node
createPage({
path: post.node.fields.slug,
component: blog-page,
context: {
slug: post.node.fields.slug,
previous,
next
},
})
}))
So this code runs, creates the pages, then I execute the GraphQL I originally posted -- and the pages aren't there.