I don't think this was known. Most people just do that via code like this:
if (keyboard_check_pressed(vk_enter)){}
The problem seems to be the fact that "Enter" key is generated as 10 (see this table:
http://www.theasciicode.com.ar/ascii-control-characters/line-feed-ascii-code-10.html) while vk_enter is actually 13 (Enter is carriage return, not line feed, but I guess on Linux they are both called so 10 could work). So can anyone on Linux confirm that Enter doesn't work? I guess it could, so the bug should only be fixed on Windows (as setting it to 13 would break Linux).
I am not sure where this can be fixed though. I think LGM is the one writing out the event information (so it is the one writing the 10, instead of 13), as events.res just does:
Super Check: keyboard_check(%1)
So anyone working with Java should check this out.