Yes, I add them with Elementor, but they are storaged in my Library. Before I remember that it could be done with the plugin Yoast SEO, but the option is not available anymore…
As the content is being added in Elementor it would be set using their controls.
When you select an Image Widget in Elementor, in the Content settings ( Left sidebar ) beside the Link field is a Cog icon – click that to reveal the nofollow option.
This also applies to the Heading Widget.
I am unsure about links within a normal text widget – that would be something you need to ask Elementor about.