It's rather atrocious that Telerik still hasn't supported passing additional parameters in the event handler 5 years later - but it turns out that there's a simple workaround, kindly identified by a Sergey T on Stackoverflow, which works well and isn't too fragile:
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I would suggest passing the target grid id as an argument to your function. Example: .Events(events => events.Error("function(args){telerikGridAraxErrorhandler(args,'myGridId');}"))
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In other words, rather than passing a string containing the error handling function name, pass a string containing a closure which is called by the Telerik control, and which in turn calls your event handler with your additional parameter(s), which is 'myGridId' in the above example.