SlickEdit Pro 2021 (v26.0.0.4 64-bit Qt5)
I observed the following:
#ifndef XXX
if symbol XXX is not defined, the enclosed text is colored as inactive code.
#ifdef XXX
if symbol XXX is not defined, the enclosed text is colored as normal code (i.e. not inactive code).
My $0.02: to be useful, those ^ colorings should be reversed.
When I do GoTo Definition of XXX, it says "No symbols found matching 'XXX'"