With macOS 15.0 and DEVONthink Pro 3.9.7
I right-click an item, select Share from the menu, and select Add to Things and a task is created in Things 3 (3.20.9).
The link included in the notes section of the task looks like this:
file:///Users/me/Databases/Main.dtBase2/Files.noindex/html/a/Test%20Share%20to%20Things.html Clicking this link produces no response.
If I right-click an item in DEVONthink, select Copy Item Link from the menu and past it in a Things task (or in any app) the paste looks like this:
x-devonthink-item://CD7F09E8-4368-483C-B04C-8A2B1260035B
And that link works to get back to the DEVONthink item (and works in iOS, too).
Both DEVONthink and Things 3 have full disk access.
Any thoughts about the Share|Add to Things method of linking a Things task with a DEVONthink item?