MicahD.

Here's a short clip explaining the concept. Basically we start with the filled line and separate it in two objects: the outer line defines one shape, the inner line defines the other. Add a centered stroke of 0,5px to the object created by the inner outline (the smaller one) so its stroke ends exactly in the middle of the two original outlines. Then expand that stroke to convert it to a shape and add it to the smaller inner object (green) so they become one. That's it. If you add a new 0.5px stroke to this object and remove its fill it will have the same exact line dimension as the original but its defines by a single path rather than two outlines.
That object i used as an example is part of a compound of three. To separate them go to menu Layer > Geometry > Divide. The result of this operation will give you the outer and inner outlines separated in two objects for all three already.
There may be other ways to get there (Contour Tool) but this one seems to be the most reliable/precise.
process.mp4

I'm recording a small video, one moment. Will explain with one of the smaller objects.
That file needs bit of clean up. Don't use it.

When I go to Export > More > Manage presets, the option to create, delete or rename is grayed out.  Any fix for this?   Working on brand new iMac, running Big Sur 11.2.3 and Affinity 1.9.1