How to create a map editor inside Unity?

Question

C++ / C#

I wanted to create a map editor for my game (2D). The functionality of this editor should be small. I would like not to create a separate program for the editor, create a map through it, save the data to a file and then import it into the unit.
I want to create (if possible) a map editor inside Unity.
Editor includes:

• Creating a checkered field
  
• Building walls. You press the button, select the cells and a wall appears in place of the cells
  

So far, here is such a small editor, but in the future it is planned to modify it.
This entire field is saved as a scene. This editor will be used only by me.
I would be grateful for examples, links to resources.
Thanks in advance!

Answer 1

Don't *get your brain: www.mapeditor.org

Answer 2

Coming soon right in Unity will be advanced functionality for collecting levels. And maybe not soon :). But it looks very cool.