This block doesn’t allow you to create a custom visual block

Variables in script are not parsed, they are evaluated. So it should be treated as if it were real javascript variables.You need to write
console.log({{My variable}})
instead of console.log("{{My variable}}")
setVariable
function
If you want to set a variable value with Javascript, the Set variable block is more appropriate for most cases.
However, if you’d like to set variables with the script blocks, you can use the setVariable
function in your script:
setVariable
function is only available in script executed on the server, so it won’t work if the Execute on client?
is checked.