Months ago, when I first tried Inkscape, I did a raster-to-vector transformation from my black-and-white line art.  Inkscape generated not only the vector lines but also vector surfaces between those lines (i.e., the "negative" space).  How did I manage to do that?  I can't figure it out again.  Need: Now after working with the resulting vector lines in Blender, I want to start working with the vector surfaces, too.  Thanks.

Not sure what you mean by "vector surface" - perhaps "color filled shapes"? These a some basic options from a Path->Trace Bitmap…:

That was it!  (I haven't found the "colorized" part of Break Apart yet, but that is a minor concern.)  I can now work with the negative-space shapes.  Many thanks.