For those purposes, you can simply copy the detail DWG file. Even without the corresponding SLD and XML file, you can always open up an archived detail DWG file, click Save Detail, and save it back into the library under any category. This is similar to another detail recovery method -- WBlock'ing a detail out of a sheet file, so that it can then be saved back into the library.
You can also grab any folder of details, along with their SLD and XML files, for the purposes of archiving or merging with another installation. In this case, note the folder would have to be restored to exactly the same location (as in, details filed under P/CO/101/HS, and thus all named starting with P-CO-101-HS-, can only be manually copied/restored back to that exact same location. You could still open the detail file, however, and use the Save Detail button to save into a different location.
In short, we've made the system as forgiving as possible in terms of being able to move and copy individual files via Windows Explorer. Moving forward, we will be adding more capability in this regard, for instance to allow simply copying large numbers of existing details into corresponding folders for easier integration.

--J