With locomotives, the QD comes from the Preload folder.
The actual list is determined by both metadata.bin files (when correctly defined) and its subordinate consist.bin files (when present), a correct listing only works when the metadata.bin points to the right consist.bin files. A metadata.bin file is not necessary, only consist.bin files are required.
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When you carefully edit both metadata.bin and consist.bin files, you can get a nice list sorted by locomotive name/type, with a sublisting by roadname. Perhaps you want to prefix the roadname with the [DLC] to differentiate between locos having different features?
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I have 3 installs, in my USA install there are no QD files, nor any locomotives in the Asset folders, that are NOT from the USA. LIkewise, UK install only has UK locomotives, Europe only has DB, SCNF, NS and other European railways.