Hello,
Unfortunately, there is no option in theme settings available to export an html block.But you can do it manually.
You can simply export the xml file from WP-Dashboard >> Tools >> Export and use Import under WP-Dashboard >> Tools to Import it.
Screenshot for Clarification: https://ibb.co/YQLnHZx
You can also do it by editing the html block and copy the code inside it and paste it inside the new html block.
Video for Clarification: https://jumpshare.com/v/7mLkGyNzXj4cy0bfs1wJ
Best Regards.
.
