you cannot debug the engine code if you are using an installed version of unreal, even if you have the source code, you can only debug it when using the editor you build, but when packaging the installed libraries are used and the code of the engine is not accessible to you. That’s why you only see the solution configuration debuggame (which means you can debug your code but not the engine’s)
to be able to debug the engine code, you need to :
clone the unreal repository of the same version you’re using (see on unreal wiki how to get access)
build the editor
launch engine/binaries/win64/UnrealVersionSelector-Win64-Shipping.exe to register the unreal version you just built
right click on your project and convert it to the built version
generate project files
open the solution, build the editor, launch it and cook your files
build in debug configuration, now when you launch the debugger for this configuration you will have access to all