Okay, so I’m trying to understand here. By looking up documentation, I see that you can place images in your file and link them to an image on your file system, so not embedding them in the file. (I’m assuming you’re not talking about inserting links to images on the Internet via URLs.) When the document opens, it loads up the image and places it in. In some apps, updating the file on the file system will update the image automatically without any intervention, and in other apps, changing it on the file system won’t update until you either manually refresh or relaunch the app.
This scenario is what I was defining as “dynamic linking.” Smart Objects (as I’m defining them in my head) are elements that are in a CC file format (like Photoshop or Illustrator). Am I misunderstanding your request for external links?
How do I vote for this a million times...