When opening an image in Nik via Lightroom, the edited version does not open back into lightroom with the edits applied
When you are done editing in Nik, you need to be performing a "Save" and not a "Save As..."
I haven't seen any "Save As" buttons in the Nik plug-ins. If the sort order in Lightroom is set to "Added order" then the image that is returned from the Nik plug-in will be displayed to the end of the film strip and not next to the original file. I always like to work in file name order so that images edited in other software will be displayed next to the original. And Lightroom always seems to default to "Added order" whenever I import new images. So I have to remember to switch the order whenever I import.