How to manage unplanned Task

How to manage unplanned Tasks in SG. e.g. Suppose I need to assign a task to an artist but that task is not in the template or in the pipeline. Can we create auto-generated Sort Order

There’s nothing automatic.
I think simplest is to manually create the Task in the Asset detail page, and assign a Sort Order value that puts it in the right place. You’d also need to update Up/Downstream Dependencies if you are using them.