How can I move Object over local axis with sliders

I found the solution :-D I will post it here for other people with similar problems. My answer was not in TransformDirection but with TransformPoint. Still not 100% sure if this is the best way to do it, but for now it works ;-)

If anybody has an idea of improving it, let me know.

 using UnityEngine;
 using UnityEditor;
 
 public class SliderTest : EditorWindow
 {
     //Pivot transform that we want to move relative to door, no matter door's orientation.
     public Transform pivotObject = null;
     //Door transform used to align pivot.
     public Transform doorObject = null;
 
     //Enable pivot control settings, enable set new pivot locattion.
     private bool changePivot = false;
 
     //Floats to control the X, Y, and Z sliders.
     private float x_axis = 0f;
     private float y_axis = 0f;
     private float z_axis = 0f;
 
     //Because we work relative to our door, we can set min / max movement to + / - half of object size.
     private float minX = -0.5f;
     private float maxX = 0.5f;
     private float minY = -0.5f;
     private float maxY = 0.5f;
     private float minZ = -0.5f;
     private float maxZ = 0.5f;
 
     //Create Menu button in example menu called slider test
     [MenuItem("Example/Slider Test")]
     static void Init()
     {
         // Get existing open window or if none, make a new one:
         SliderTest window = (SliderTest)EditorWindow.GetWindow(typeof(SliderTest));
         window.Show();
     }
 
     //Use this to repaint the editor window constantly.
     void OnInspectorUpdate()
     {
         this.Repaint();
     }
 
     void OnGUI()
     {
         EditorGUILayout.BeginVertical();
         GUILayout.Label("Base Settings", EditorStyles.boldLabel);
         EditorGUILayout.Space();
         EditorGUILayout.Space();
         //Create input fields to load in door and pivot objects.
         doorObject = EditorGUILayout.ObjectField("Door:",doorObject, typeof(Transform), true) as Transform;
         pivotObject = EditorGUILayout.ObjectField("Pivot:", pivotObject, typeof(Transform), true) as Transform;
         EditorGUILayout.Space();
         //Only show buttons and settings if both door and pivot objects have been loaded.
         if (pivotObject && doorObject)
         {
             //GUI.enabled controls if GUI objects are active or grey and is controlled by boolean
             //If we are not in pivot mode, this will grey out buttons and settings.
             GUI.enabled = !changePivot;
             //If this button is pressed, the pivot model will be aligned with the door.
             if (GUILayout.Button("Reset pivot to object"))
             {
                 //Get location and rotation of the door and pass them on to the pivot object.
                 pivotObject.position = doorObject.localPosition;
                 pivotObject.rotation = doorObject.localRotation;
                 //Reset the X, Y and Z sliders, so the pivot stay's / starts in the center.
                 x_axis = 0f;
                 y_axis = 0f;
                 z_axis = 0f;
             }
             GUI.enabled = true;
             //Button to enable / disable pivot editing mode
             if (GUILayout.Button("Edit Pivot"))
             {
                 changePivot = !changePivot;
             }
 
             GUI.enabled = changePivot;
             //Read the slider values.
             x_axis = EditorGUILayout.Slider("Slider X", x_axis, minX, maxX);
             y_axis = EditorGUILayout.Slider("Slider Y", y_axis, minY, maxY);
             z_axis = EditorGUILayout.Slider("Slider Z", z_axis, minZ, maxZ);
             GUI.enabled = true;
 
             //if we are in pivot edit mode
             if (changePivot)
             {
                 //create a new Vector3 with the sliders as input
                 Vector3 relativePos = new Vector3(x_axis, y_axis, z_axis);
                 //create a new Vector3 and fill it with the relativPos transformed into worldspace.
                 Vector3 exactPos = doorObject.TransformPoint(relativePos);
                 //Update the pivot position with the new world position relative to the door :-).
                 pivotObject.position = exactPos;
             }
         }
         EditorGUILayout.EndVertical();
     }
 }