I wrote a very simple blink and external LED program in the Web IDE and tried to get it to work in the Workbench with no luck. I just copied and pasted the code.
It claims that HIGH has not been declared in this scope.
The error message states High to be the problem, although I cannot see where that came from it needs to be spelt HIGH - C/C++ is case sensitive.
Additionally, don’t rely on IntelliSense. Rather run a proper build and observe the actual build messages. To see them you may need to turn on verbose logging.