How breakpoint engine source?

I know engine use UnrealBuildTool compiling source to binary .
I want to know how debug and breakpoint one by vs.

If you want to debug UnrealBuildTool, you first need to set the command line arguments in the Debug tab of the UnrealBuildTool Properties. These are documented in /Engine/Build/BatchFiles/Build.bat Then set UnrealBuilTool as the Startup project and hit F11 VS will compile and run UBT and then break at the first statement. You can set breakpoints in theC# code the same way as C++.

I simply set the build configuration to “Debug” or “Debug Game” and hit F5. Breakpoints work then (both for the game code, and the engine code). But be warned, the editor runs super slow in debug mode.

thanks a lot.

oh! because of the slow.