I am referring to collapsible headings when exported to PDF

Hi Larry

Thanks for posting in the Lucidchart community! Unfortunately it is not currently possible to collapse/expand sections in a PDF export. If your use case would work with a published document instead of a PDF export you could create portions of your diagram that expand and collapse using layers and hotspots--this help center article walks through how to configure this. If this isn't a good fit for what you are hoping to do please add this feature (and your use case for it) to our feature request form.

I hope this helps! Feel free to let me know if you have any further questions.