Document sets provide an easy way to group subsets of cases that share certain characteristics. To create a set, I examine the codebook, and transform codes of interest into document variables. The process is easy -- simply right click on the code and select "transform into document variable." The code remains a code, but it is now also a variable and can be used to further differentiate the data.
Once the variable is created, navigate to "Mixed Methods" and select "Activate by document variables." This will open a dialog box and you can select the variable you created. Since it is possible that a code will have more than one segment in a document, set the condition to "variable name > 0" so it will activate all documents that have the code in it. But before processing it, make sure you selct "Activate and create set."
Now you will have a new document set that you can use to select documents that meet specific criteria