First, let me state that GMLive.gml is a life-saver. Without it I don't think I would use GameMaker since the development process would be too slow. Even if it cost $200 I would pay for it.
Now, it's commercial extension, so I bring two suggestions, for quality-of-life improvements.
The point of using GMLive.gml is to cut down development time by partially eliminating recompiles. However, often while live coding you have no clue whether an error has crept into the code, since the program is silent. You're supposed to check the output log, but by doing that you may be spending unnecessary time, not to mention it's cumbersome. Actually, I often would rather recompile than check the log, which betrays the purpose of the extension.
So, wouldn't it be great if an alarm sound is played whenever GMLive detects an error? That way you will only check the log when you know there's an error.
It would also be nice if a following like macro is added to obj_gmlive:
#macro LIVE if (live_call()) return live_result;
By typing LIVE rather than the whole function it makes things easier to read and use.
Finding or creating good, free sound effects shouldn't be a problem, but I made two that's better than nothing for your instance here.
Thank you for your work!