Different demo share buttons in each demo

We're able to set an account-wide demo share button text/url, but each demo category is better suited to be different.

For example: marketing demos are better suited to say something like "Start Free Trial," while onboarding guides can say "Visit Help Center," etc.

Showing a logged-in customer a popup embedded demo with "Start Free Trial" on the top-right doesn't sit right, while removing it is a lost CTA opportunity for marketing use cases.