To clear or reset variable values in Blockly within Synthiam ARC, you don't have a direct "delete" command like you might in text-based programming languages. Instead, you manage variables by setting them to a new value or resetting them. Based on your script, it seems you're trying to manipulate and then delete a variable, which isn't directly supported in Blockly the way you might expect from JavaScript or Python.

Here's how you can achieve similar functionality in Blockly:

1. Setting a Variable: To set a variable in Blockly, you use the "set variable" block. You can initialize your test variable to 0 by dragging a "set variable" block and typing test as the variable name, then attaching a number block with the value 0.

2. Printing to Console: To print to the console, you use the "print" block and attach text or variable blocks to it. For printing "Hello World" or any other string, you simply attach a text block with your desired string to the "print" block.

3. Manipulating Strings and Variables: To concatenate strings or add variables, you use the "create text with" block or "math" blocks for numerical operations. For example, to add test to itself, you would use a "set variable" block for test, and in the value part, you use a "math" block to add test to test.

4. "Deleting" a Variable: In Blockly, you don't delete variables. If you want to reset or clear a variable, you set it to a new value. For example, to "clear" test, you might set it back to 0 or to an empty string "", depending on your use case. There's no direct equivalent to the delete keyword from JavaScript in Blockly.

5. Handling Undefined Variables: If you try to print a variable that hasn't been set or "deleted" (reset), Blockly won't throw an "undefined" error like JavaScript. Instead, it will print null or nothing. To avoid confusion, ensure your variables are initialized before using them.

Here's a simplified example of what you're trying to do, translated into steps you might take in Blockly:

• Set test to 0.
• Print "Hello World".
• Print the length of "Hello World" (you would need to use a block that calculates the length of a string).
• Print "hi + I'm a robot" (use the "create text with" block for concatenation).
• Add test to itself and set test to the result.
• Print test.
• To "delete" test, set it to 0 or an empty string.

Remember, Blockly is designed to be more straightforward and doesn't directly expose some of the lower-level operations like deleting variables. Instead, you manage your program's state by setting and resetting variables as needed.

Your code is correct. Read it again and see that you delete the variable, but then try to print it. You can't print a variable that doesn't exist.

delete test; < - DELETED VARIABLE!
print(test); <-  VARIABLE IS DELETED!

You need to create the variable again if you want to use it

delete test; <- DELETE VARIABLE
test = "banana" <- ASSIGN VALUE
print(test); <- PRINT NEW VALUE

*Note: I edited your question to add CODE formatting because you did not do that. And it can't be understood without correct formatting.