Hi Terry
In the lightview view I rate the images and select them.
It is a great advantage to have an overview with smaller previews in centre view, where I can quickly jump to an image if I want to look at it more closely. In full screen mode (shortcut F or W) I lose the overview, so I have to switch back again and again while a “wrong” picture (left from the last darktable edit) is permanently displayed on the second monitor.
It’s true, I can also go further in the filmstrip in the darktable view, but that takes far too long, because the basic modules always have to be loaded first.
Probably Nilvus is right and it just hasn’t been programmed. It would be really a very simplifying feature, and the structure is there (selection of the second monitor, its ICC profile management, etc.).
I am surprised that no one else has complained yet. All RAW developers work with this standard of having an overview with small previews and showing the selected image in large format on a second monitor (if there).