Libtooling in Visual Studio

I was wondering if there were any existing
implementations that I could use for reference or

advice that could point me in the right direction.

At the risk of mis-interpreting what you mean, but shouldn’t you just use llvm-lib.exe? The LLVM Toolchain Plugin let’s you do just that [use llvm-lib.exe from the IDE]. If you need/want to use that plugin in VS2019, just shout.