Hello, and thank you for your question :D
If you want to create a visual programming language, you probably don't want to create something like Blockly. You probably want to *use* Blockly!
From the
dev site home page: "The Blockly library adds an editor to your app that represents coding concepts as interlocking blocks. It outputs syntactically correct code in the programming language of your choice. Custom blocks may be created to connect to your own application."
There are people that use Blockly to create CS curriculum, exploratory coding environments for kids, interfaces to configure web stores, encode laws, automate factory processes, etc. So if you want to create a blocks-based programming language, whatever the domain may be, Blockly can probably handle it =)
I hope that helps! If you have any further questions please reply!
--Beka