For more detail this asset from the Unity Asset Store: Click Here
This is a paid asset, but now you can download UI Editor for FREE, Please keep in mind this package is provided only for learning purposes or to be able to test before buying the product, NOT FOR COMMERCIAL PURPOSES.
UI Editor v1.3.1
UI Editor is a decidated editor window that allows you to build user interfaces with ease and speed.
Features
∙ Seperate Editing Window
∙ Completely removes UI from 3D scene
∙ Context Menu
∙ Alignment Tools
∙ Arrow Keys Nudging
∙ Grid and Snapping
∙ Drag & Drop controls toolbox
∙ Drag & Drop images from project folder
∙ Edge Snapping
∙ World Background Rendering
∙ Improved Workflow
∙ Full Source Code Included
For questions and support please visit the unity forum thread.