Alt Text for Thumbnail Images

I have a flipbook as a catalog and I’m embedding the shortcode like this:

[3d-flip-book mode="thumbnail-lightbox" id="3841" lightbox="dark" thumbnail="https://mysite.com/wp-content/uploads/2020/09/home-catalog.jpg"][/3d-flip-book]

I don’t see anywhere here where I can add alt text for the thumbnail image, which is a necessity for accessibility. Is there a place I can incorporate that?

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