Create a floating div container macro

I primarily use Confluence to maintain documentation for engineers to consult. I currently make use of the page layout feature to create a right side-bar where I put the Table of Contents.

For long documents, this side-bar section is unused space. It would also be useful for users to have the ToC scroll with them as they read further down the page so they can quickly jump to other sections that are relevant.

This could be enabled with a Floating Container macro similar to the Expand macro.