You don’t really need it to match the bone per se, you want it to leave Blender with no transforms off world 0,0 of its own. That makes it much easier to attach it to things in the engine without it flying off into random space.
That way it just inherits the transform of its new parent, and doesnt add anything extra of its own (visually) that is a result of being exported offset from its own origin.
Beyond that you have the question of which axis the bone is oriented along, which depends on how your rig is built and I have no knowledge on the specifics there. But thats why I suggested creating sockets on the bones you want to attach to - since you can position and rotate these independently in the editor and they will stay attached relative to their parent bone, once you have a cleanly exported mesh piece with its origin at world 0,0 in Blender, you can preview it attached to the socket, move/rotate the socket until your mesh is exactly where its supposed to be relative to the bone, and then when you attach for real in the Blueprint you know it will be correct.
As long as the mesh itself has no unwanted transforms away from the origin at export, the socketing/previewing process in the editor should provide the link you need between bone and mesh that lets you visually line everything up, with a bit of work.
You just need to make sure that the area of the mesh that should visually be its pivot when animating is sitting at the world origin when you export, which you can do by setting the object’s origin to that visual pivot point in Blender, and then snapping the whole object to grid 0,0.
Its essentially the same principle as attaching a sword static mesh to a characters hip, or a gun to their hand. You don’t try to export the weapon mesh in perfect relation to its target skeleton bone, you export it with the area to be attached at 0,0 and then use a socket on the hand or hip bone to place it relative to that bone in the editor.
Setting up the sockets would be kind of a pain in the ■■■ if you have a really complex skeleton and many mesh parts, but it seems the most hassle-free way of accomplishing what youre trying to do that I can think of since lining everything up can be done visually with every socket having its intended mesh previewed and positioned directly in the skeleton editor.
There might be other ways to do this, but thats how I would go about it for the sake of sanity. If you are able to make it work with inverse transforms though, power to you!
Apologies if I repeated myself here, I don’t want to try and teach grandma to suck eggs as the saying goes - I just feel like you may be making this harder on yourself than it should be.
