How do I change the control’s attribute in the form?

You can do that through the API method:

DWKitApp.API.rewriteControlModel("controlName", gridModelRewriter);

where controlName is the name of the control, and gridModelRewriter is the function that changes the control model.

var gridModelRewriter = function (model) {
    //TODO Change the model of the control
    Model.parameter1 = value;
    return model;