it seems you have to merge two directories before importing into the destination darktable database.
- directory/ies: you copy images from your camera to your laptop for an initial edit with darktable, so that directory/ies contains also xmp files with the history stack
- directory/ies: you copy the images from the camera/sd cards to their final destination on your nas
If the directory structure doesn’t differ, you can use rsync or some gui tools (e.g. beyond compare) to copy the xmp files from 1. to 2.
Importing into primary darktable from 2. should be done after the xmps are copied.
If you already imported then you need to update the file date for your laptop xmps before copying so new xmp files can be detected on next darktable start.