Your LODs should also be named identical to the mesh, so adding a suffix to a mesh within a set of meshes of the same item makes little sense…
If your meshes are just called low_1mwall instead of 1mwall to differentiate a half wall (or anything similar).
First, may I suggest changing low to a height value? 1mx1m_wall vs 2mx2m_wall is probably a lot easier to understand for whomever comes next to the project.
Second.
Yes, the low needs to be within the collision hull for it to import correctly.
UCX_low_1mwall
And if there’s any
low_1mwall_LOD_0
(Within an empty group of the same name if in blender)
Another note. The engine tends to ignore/discard collision boxes that touch each other… kinda hate that since it makes it near impossible to section off an item easily / you need to move some vertices or shrink/enlarge the hull…