Unfortunately, at this time the location cannot be changed through the public API. What would expect from an API for that? Like, Grid.Editing.ErrorMessage.Placement, which would have a bunch of alignment options like the .NET ContentAlignment enum?
Or would expect something else? Anything else besides that? Color, css classes, size, etc?
Thanks. Once we know better what you (and others, I'm sure) want here we can deliver an update in an upcoming release.