Is there a way to remove the airspace shading so that only the outlines show?

Well, sort of.

You can customize the map display in a configuration file: https://www.littlenavmap.org/manuals/littlenavmap/release/2.6/en/CUSTOMIZE.html#map-display
Set the fill color for all airspace types to start with "#00...." instead of "#30...".

For example change

[Airspace]
AlertFillColor=#30fd8c00

to

[Airspace]
AlertFillColor=#00fd8c00

The color format is explained in the user manual chapter I linked above.

Alex

Perfect.  Exactly what I was looking for.  Thanks!