Display CMake variables without running CMake on a CMakeLists.txt file or manually inspecting config.cmake?

You asked: (1) Is there an easy way to display these variables without having to run cmake on a CMakeLists.txt file, and (2) without having to manually inspect the config.cmake file?

I can give you a yes answer to (2) but it does require that you (re)run cmake. But since you can re-run your cmake configure step by simply executing cmake . in the build directory, re-running cmake should not keep you from trying this approach. My answer is given in this SO answer and uses the get_cmake_property command. Here is that code encapsulated into a cmake macro, print_all_variables, so I can use it when debugging my cmake scripts.

macro(print_all_variables)
    message(STATUS "print_all_variables------------------------------------------{")
    get_cmake_property(_variableNames VARIABLES)
    foreach (_variableName ${_variableNames})
        message(STATUS "${_variableName}=${${_variableName}}")
    endforeach()
    message(STATUS "print_all_variables------------------------------------------}")
endmacro()

The macros are invoked with same syntax as cmake functions:

print_all_variables()