RaindropViewer/Assets/Editor/SimpleEditorUtils.cs

// https://answers.unity.com/questions/441246/editor-script-to-make-play-always-jump-to-a-start.html
// IN YOUR EDITOR FOLDER, have SimpleEditorUtils.cs.
// paste in this text.
// to play, HIT COMMAND-ZERO rather than command-P
// (the zero key, is near the P key, so it's easy to remember)
// simply insert the actual name of your opening scene
// "__preEverythingScene" on the second last line of code below.
 
using UnityEditor;
using UnityEngine;
using System.Collections;
 
[InitializeOnLoad]
public static class SimpleEditorUtils
{
    // click command-0 to go to the prelaunch scene and then play
     
    [MenuItem("Edit/Play-Unplay, But From Prelaunch Scene %0")]
    public static void PlayFromPrelaunchScene()
    {
        if ( EditorApplication.isPlaying == true )
        {
            EditorApplication.isPlaying = false;
            return;
        }
        EditorApplication.SaveCurrentSceneIfUserWantsTo();
        EditorApplication.OpenScene(
            "Assets/Raindrop/Bootstrap/BootstrapScene.unity");

        EditorApplication.isPlaying = true;
    }
}