You are passing V1 as a variable in the workflow.
Import Arguments is designed to show arguments. Create V1 as an argument in your workflow sequence.xaml and it will show up in import arguments. ALso if you create an IN argument it will allow you to pass the value into the workflow and if you create an OUT argument it will allow you to pass value out of the argument. IN/OUT will allow you to pass value in and out of the workflow.
See screenshots below:
