I think people are looking way too deeply into the Dark Wheel toast. Remember, the Dark Wheel doesn't actually know Raxxla's exact location; they're just dedicated to looking for it.
"The whisperer in witchspace, the siren of the deepest void" just means that Raxxla is an irresistably tempting prize. You know it's out there somewhere and it's like it's whispering in your ear, tempting you to come find it.
"The parent's grief, the lover's woe, and the yearning of our vagabond hearts" refers to the search for Raxxla consuming the lives of those who seek it, to the point where they abandon their loved ones to go look for it. The Dark Wheel are vagabonds, aimless wanderers, because they have given up everything in the name of finding Raxxla.
There is one line in the toast that I think is worth investigating: "the jewel that burns on the brow of the mother of galaxies." While this could just be more flowery prose saying that Raxxla is the most valuable thing in the galaxy, it's strange to refer to the Milky Way as "the mother of galaxies" since it has no associations with motherhood. I believe that this actually refers to the constellation Cassiopeia, the mother of Andromeda (i.e. the Andromeda galaxy) in Greek mythology. I've visited some of the main stars in the constellation itself and found nothing of note, but there's still plenty of room in that section of the sky for Raxxla to be hiding in.
The Dark Wheel doesn't know where Raxxla is, but maybe they do know it's somewhere in this area. It's still a huge area to hide in but it's considerably narrowed down versus the galaxy as a whole.
(I don't actually know anything about astronomical coordinates or geometry so my attempt to illustrate the bounds of the region may be entirely wrong)