Simple Blender Like Camera Controls in the Scene View

SceneViewCameraHandler.cs

using UnityEngine;
using UnityEditor;

[InitializeOnLoad]
public static class SceneViewCameraHandler
    {
    public class SceneInfo
        {
        public SceneView view;
        public Camera camera;
        }

    private static Event e;

    private static float rotValue = 15f;

    private static SceneInfo scene = new SceneInfo();
    private static SceneView view => scene.view;

    static SceneViewCameraHandler()
        {
        SceneView.duringSceneGui -= AddCameraControls;
        SceneView.duringSceneGui += AddCameraControls;
        }

    private static void AddCameraControls(SceneView view)
        {
        // Set to curr view
        scene.view = view;
        scene.camera = view.camera;

        //Get Event
        e = Event.current;

        if (e.type == EventType.KeyDown)
            {
            //Rotation
            if (e.keyCode == KeyCode.Keypad5)
                {
                view.orthographic = !view.orthographic;
                e.Use ();
                }

            //Snaps
            DoKeyRotate (KeyCode.Keypad1, Quaternion.Euler (0, 0, 0));
            DoKeyRotate (KeyCode.Keypad3, Quaternion.Euler (0, 90, 0));
            DoKeyRotate (KeyCode.Keypad7, Quaternion.Euler (90, 0, 0));
            DoKeyRotateRelative (KeyCode.Keypad9, Quaternion.Euler (0, 180, 0));

            DoKeyRotateRelative (KeyCode.Keypad4, Quaternion.Euler (0, rotValue, 0));
            DoKeyRotateRelative (KeyCode.Keypad6, Quaternion.Euler (0, -rotValue, 0));
            DoKeyRotateRelative (KeyCode.Keypad8, Quaternion.Euler (rotValue, 0, 0));
            DoKeyRotateRelative (KeyCode.Keypad2, Quaternion.Euler (-rotValue, 0, 0));
            }
        }

    private static void DoKeyRotate(KeyCode keyCode, Quaternion rotation)
        {
        if (e.keyCode == keyCode)
            view.LookAt (view.pivot, rotation);
        }

    private static void DoKeyRotateRelative(KeyCode keyCode, Quaternion rotation)
        {
        if (e.keyCode == keyCode)
            view.LookAt (view.pivot, view.rotation * rotation);
        }
    }