an x-devonthink-item link is not portable in the sense “across platforms” (think Windows) or machines (think “another Mac”). It is not even portable to another Mac that is running DT.
But nor are other links. They’re just that - links. Pointers to another entity located somewhere™. If that location is on your local machine (and your machine is not running a server that would make the location accessible from the outside), nobody but you can use these links.
That is not correct generally. If you use an absolute path for the URL (something like /Users/me/Images/image1.png
(perhaps with a leading file://
protocol), the image should display as long as you do not move it to another location in the filesystem.
Links are links. There’s nothing you can do about them being susceptible to breakage.
Exactly – breakage.