Hi:

If you first create a context diagram, then creating a written scope statement is a easy.  You just simply, referring to the context diagram, say, for example, the system inputs A data from outside entity B and outputs X data to outside entity Y, etc. etc.  The sum of all these inputs from outside entities (i.e., systems or people) and outputs to outside entities is your scope.

If, especially for larger scale systems, you try to jump first thing into creating a text based document, no document format is going to help.

Problem:  For larger scale systems no one is knowledgeable enough to jump first thing  into creating a context diagram.   You need to first create and verify lower level data flow diagrams and then summarize them into a context diagram.  (This is the "catch" to scoping larger-scale systems that few want to admit to.)

Tony