Feature Request: Custom Thumbnail for Demo Cards

It would be great to have the option to manually upload or select a custom thumbnail for each Supademo card in the dashboard/library.

Currently, the card thumbnail appears to be generated automatically from the demo content, while the Custom Meta Image only affects the shared link preview.

It would be very useful to have a separate “Card Thumbnail” setting, allowing users to:

• Upload a custom image;

• Select one of the demo steps as the thumbnail;

• Use the chapter cover image as the thumbnail;

• Preview the thumbnail before saving.

This would help keep the Supademo library more organized and visually consistent, especially for teams that create many demos and follow a specific branding standard.

Suggested location: Demo Settings → Appearance → Card Thumbnail.