The meta/list/prop param of action=query are multi, but with ApiSandbox you can only choose one of them.
Please allow selection of multi modules and selection of mulit list/prop/meta at the same time.
meta=userinfo&prop=templates&titles=MainPage is a valid request
generator=templates&titles=MainPage&prop=templates|images is also a valid request, but it is not possible to create it with ApiSandbox
Version: unspecified
Severity: enhancement
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=45630