Traditionally this feature has been handled by DTP software as a separate step. In many ways it does make more sense to order and layout in the document your are creating as the media, size, margins etc might affect your choices.
I have wished for a visual rename tool for a long time. A tool that displays a grid of thumbnails and allows you to order them and then rename the files by adding a prefix number. It should also be able to open a folder with number-prefixed files and allow for reordering and replacing the prefix number.
Geeqie has a similar feature but instead of renaming files it outputs a text file. It’s not as convenient as a rename.
Since darktable has DAM features, and sort of encouraces a RAW centered workflow, I see the use of being able to create ordered collections. The utility both process and output oriented.
Thinking about your images, planning their display and adjusting settings depending on context and order.
A new export option that prefixes the filename with a number and perhaps the collection tag.