Some Shorthand plans offer additional publishing options including the ability to reference specific image file locations and to add custom HTML to the <HEAD> tag of a story. These actions take place when the story is processed for export or download.

If your plan includes these options, you'll find them in the SETTINGS panel accessed through the top-left of the story editor.

Asset URL (disabled by default):
If you add an asset URL, then in published stories (NOTE: Not preview) all relative links to assets (./), will be replaced with the link specified.  For example:

Will change ./ to https://example.com/assets/