As per limitations section, GMLive treats macros as expressions instead of tokens.
In current versions of GameMaker, "global" is no longer a "value" - for example, you can't do
var q = global; trace(q.test);
so that's why that doesn't work in GMLive either (because "G.test" would evaluate "G" first, and only then try "(global).test").
I can potentially make it treat "global" specifically as an intermediate value (so long as .field access is done on it in the end) but it'll be a few days before I can properly look into that.