Extensions in unity

Hello
Just wonder , how these extensions Created-

-> https://www.assetstore.unity3d.com/en/#!/content/3558
-> https://www.assetstore.unity3d.com/en/#!/content/55649
-> https://www.assetstore.unity3d.com/en/#!/content/18025
etc.
Like this is not just custom script , it's way advance stuff.
Pls tell me -
->How developer created this mesh editing possible inside unity (realtime)?.
->Every tool is very different then implement it using any special unity feature(or it's just UI and Custom scripts) and how can i create such things ?
->How to get tutorials to make these things?(this is advance stuff so no tutorials found)

 

Hey,

this is a good start for the UI stuff: http://docs.unity3d.com/Manual/editor-EditorWindows.html
For the functionality: It really depends on what you want to do. But once you got the EditorWindows setup, it basically is nearly the same as doing that for runtime

 

Th

thanks pal