Board Thread:Support Requests - Getting Technical/@comment-24553580-20151010043724/@comment-2093602-20151010090612

I looked at some new wikis and it doesn't appear to be enabled by default. You can check it on Special:Version if you have to.

That said, Lua templates (enabled by default) are almost always a better option than the variables extension. Perhaps if you explain what you want to use the variables for, someone could see if it's better off in Lua.