Is there any advantage to create attributes with the Environment Edit node instead of using Attribute nodes? I can see a flag in the variables created by the Environment Edit node, any use with it?

The attributes created using the environment edit are exported to the environment of out of process jobs run by the scheduler. It adds the “export” flag onto the attributes. Generally that node is used if you have attribute values that you want to pass to some external program or shell script that's controlled by env vars.