First make sure that the code you are after is in the Description Key Set (DKS), if it is then do the steps below. If it isn't you will need to add a new code to the DKS so it can be used below as well.
If you want to create a new code in the Stringer Settings this is how you would do it below.
-Click on Stringer Settings (make sure you have your CSV file set as current) -Find a code that is going to be about the same as the one you are adding in - click on the new button bottom left
-This will make a copy of that code - double click in the code and change the code to what you require
-Then select what TYPE of line it is going to be (3d Breakline, 2d Join Only or 3d Polyline) -Select the 2d layer you want the string to go on -Select the 3d Layer you want the 3d layer to go on (3d layer is normally only 1 layer as it is only required to create the breaklines in the drawing) -Click OK
Once that has been created, go and click on Join All Codes again and now it will be strung in the drawing and also added as a breakline in the surface. That code will now always be in the Stringer Settings CSV file for the next time you use that code.