CommandStudio is an editor that let you write complex sequences of command blocks and easily import them into Minecraft. It has a lot of convenient tools which will make your life easier.
You can use it at: http://commandstudio.github.io/commandstudio/
Further informations on how it works at: http://commandstudio.github.io/commandstudio/manual/
Come and discuss about CommandStudio at the dedicated Discord server: https://discord.gg/Eg5r99u