Is there a way to exclude the main page markdown to shown in the drop down in docusaurus?

For example: I have: myDir/index.md myDir/first.md myDir/second.md

if all the md file are generated and I can't manually list them in the sidebar, only can use autogenerated.

So how can I avoid the index.md content only shown in the myDir main page, not the myDir drop down?