vcproj-debug-options is what you need to set the executable path in cases where it cannot be resolved automatically. However, I am getting a Slick-C stack when I invoke command, which may be why it isn't saving the values correctly. I am working on a hotfix to address the Slick-C stack.
As a temporary workaround, and you are comfortable manually editing XML you could manually add the configuration directly to the SlickEdit project file (.vpj).
For each project configuration there is a <Config> node:
<Config
Name="Debug|Win32"
Type="vcproj"
DebugCallbackName="windbg"
OutputFile=""
CompilerConfigName="Visual Studio 2010">
...
</Config>
<Config
Name="Release|Win32"
Type="vcproj"
DebugCallbackName="windbg"
OutputFile=""
CompilerConfigName="Visual Studio 2010">
...
Before the end of each Config node, you can add these properties specifically for WinDbg:
<List Name="WinDbg Options">
<Item
Name="OutputFile"
Value="C:\work\project\Debug32\executable.exe">
</Item>
<Item
Name="SymbolPaths"
Value="">
</Item>
</List>
</Config>
Where OutputFile is location of the executable and SymbolPaths are locations of PDB files.
If you are still unable to create process after setting output file, it could be a problem finding the Debugging Tools for Windows paths or the correct dbgeng.dlls.