Elementor now allows any of its link fields to have the nofollow attribute added, by simply clicking the gear next to the URL field, and ticking the checkbox, as shown in the image.
Not Available In Text Editor Element
Keep in mind though that this only applies to elements in which Elementor is supplying an actual link field. This won't work in Text Editor elements, because it's not a part of the core TinyMCE editor. No worries though. You can add the checkbox yourself via an extra plugin.
Use A Plugin For Text Editor Availability
Install the Title and Nofollow For Links plugin, and you'll have the checkbox option available in the text editor as well. Again, just click on the gear to get to the additional link options, and you'll see a new checkbox there, as shown in the image.