I used the Nikon multiple expsosure feature with raw files some years ago, and I suppose I should try it out again when the time and place are right.
Push your creativity further with image overlays — Enhanced multiple exposure options
The D850’s multiple exposure function is more versatile than ever before, allowing photographers to explore their creativity further. The camera now saves all pictures shot in this mode, so you can use individual images for other purposes as well.
It is also now possible to confirm each picture during shooting, as well as the overlay image being created.
If your last shot doesn’t meet your satisfaction, you can delete, reshoot and replace it easily. Furthermore, the camera lets you select a picture stored as RAW (L) on your memory cards for use as the first image of the overlay. Lighten and darken overlay modes are also now available.