Is there a way to customize how a table will be created when using table markdown? Specifically, I would like to add scope attribute as suggested in webAIM WebAIM: Creating Accessible Tables - Data Tables
No, there is not.
You’ll need to include HTML in your markdown page.
Is it possible to use Markdown Render Hooks? I am trying to find an example on how render hooks works.
No, it is not. Render hooks are available for headings, links, and images only.