Action to "Open containing folder in file manager" (to view an image file in its context for advanced file management operations)
Sometimes I want to do some advanced operations or file management that may not be possible with gthumb, and best done with a file manager app. For those situations, I would like to be able to right-click on an image (or also use the menubutton) in single image/slideshow view, or a selected image in gthumb's folder contents grid browser view, to "View in File manager", where it would call Nautilus (or whatever file manager is the default) to open the containing folder with the relevant file preselected/scrolled-to (I'm not sure how this is done, but other apps like Firefox, "Eye of GNOME" and Shotwell, are able to do exactly that).
This is already partially implemented from what I can see in gthumb 3.12.2 (if you right-click a folder in gthumb's treeview sidebar, you can "Open in the File manager"), but I'd like the behavior to be extended to the image browser and the image view for a selected/shown image (and for the file to be preselected in the resulting file manager window).