I already had a tasks.json in my project, so the new extension didn’t overwrite it. which in turn meant that nothing was happening.
I tried it out on a different project that doesn’t have the tasks.json file in the project and I have the build menu appearing now.
I think that this is going to be great, when it’s all working - still a bit of playing for me to get it going.
c:\path\main.h:32:21: error: ‘Serial5’ was not declared in this scope