Custom Attributes not showing on link

I have created a comparison table with a button under each column. I want to add a data-* attribute to these buttons. In the Link options there is the Custom Attributes section, which is available on all Links in Elementor. I’ve added an attribute like it says: key|value (e.g. data-package|1), but it doesn’t show on the frontend.

I’ve added the same attribute to a standard Elementor button link and it worked fine.