Exporting Scrivener projects to Devonthink

I suppose one immediate question is: does Devonthink have any standard or easy way of importing multi-field data? Does it have a format or convention (like CSV) that would make it so importing such a file not only establishes its content and title, but would set metadata values to the item?

If it does have a file format, or structured text file approach for doing that, then it is likely Scrivener can create it. That example demonstrates a more complex interchange format, using the JSON syntax, but sometimes complex examples can illustrate the spectrum of capabilities you have. If for example CSV is something you could use, well, if Scrivener can make that, it can surely formulate data onto a line with some commas or tabs in between them.

Whatever the case, getting trapped into Scrivener is nearly impossible, unless one imposes that upon themselves as a constraint.

Another approach: the Export feature does have a metadata checkbox, which creates a .txt file alongside the main content file(s). This uses a consistent format that AppleScript (which DT supports) could work upon.