I have found that it is easier to manage my files from within Darktable.
When I cull or edit images I hit R (marks the image rejected), later in lightroom I chose set the filter to "View only rejected", press Ctrl-A, in Selected files click delete (trash). Actually i don't click delete, I have define a keyboard shortcut for the last action, just shift-Del and Images are in the trash.
This removes images from DT database and from the file system. It uses the system trash so you have the option of restoring if you regret deletion.