Hi @Sylvain_Page - attachments are currently hard to access safely from custom widgets. There’s an update coming very soon to resolve this. Watch this space!
If your document happens to be publicly viewable, then you can use image source urls like https://docs.getgrist.com/api/docs/DOCID/attachments/NNNN/download where NNNN are the ids stored in the attachment column (in your table they’d be available as $A.id). But most docs aren’t publicly viewable, and access to the attachment columns from a custom widget will be denied - hence the update we are working on.