I have created a feature with

            var feat = featMgr.InsertMacroFeature3("Helix", typeof(HelixFeatureMacro).FullName, null, (paramNames), (paramTypes), (paramValues), null, null, editBody, null, opts);

and have 3 numeric textboxes with callbacks on the IPropertyManagerPage2Handler8 interface. The PMP has a reference to the feature as _Feature but I can't find any API to set the parameters I declared using InsertMacroFeature3

        public void OnNumberboxChanged(int id, double val)

        {

            switch ((HelixPMP.ControlIds) id)

            {

                case HelixPMP.ControlIds.Pitch:

                    // Set pitch here for feature _Feature

                    break;

                case HelixPMP.ControlIds.Radius:

                        // Set radius here for feature _Feature

                    break;

                case HelixPMP.ControlIds.Height:

                          // Set height here for feature _Feature

                    break;

                default:

                    throw new ArgumentOutOfRangeException(nameof(id), id, null);

            }

        }

Regards

Johannes.