As a workaround, I discovered you can at least change what appears in the body text area for a parameter.
Within the IOperation filter that sets your example, you can search through your Operation, find your operations body data parameter that holds the model and set the parameter's "default" property value to a JSON object.

While this won't fix your example value on the right, this will at least provide a way to get an example in your request data.
Hopefully this helps someone stuck in .Net Framework with Swashbuckle.
Edit: Here's some vb code I use to set the data parameter:
Dim dataParameter = operation.parameters.Where(Function(z) z.name = "data").FirstOrDefault()
If dataParameter IsNot Nothing Then
'Since upgrading to v5.6 for microsoft webAPI packages (at least that's the most likely reason), it appears to have broke request example JSON rendering on the now out of support Swashbuckle for .NET framework
'If I set the default here, I can at least get it to load in the body text area, which is a decent workaround.
Dim requestExample = GetRequestExample(operation.operationId)
If requestExample Is Nothing Then Controller.Base.ThrowInternalError($"Issue with endpoint {operation.operationId}: No response example and no request example given. Most likely, this is because you have a custom endpoint with a data parameter and did not put an example in ExamplesOperationFilter.GetRequestExample()")
Dim requestExampleProvider = DirectCast(Activator.CreateInstance(requestExample), IProvideExamples)
dataParameter.default = FormatAsJson(requestExampleProvider).ToString
End If