It looks like that for now, the SE strings are broken out by section, but only by collection. Thus, you could get the strings on the SE 1 collection, but that would include both the solo strings (which you don't want) and the orchestra strings. There does not appear to be any way to break the SE orchestra strings out separately.
Since you have the full solo strings set, I would suggest saving for the full orchestra strings set, if at all possible. Especially for layering, you might find the SE orchestra strings articulation set rather limiting. Depending on your composition goals, getting either the full chamber strings might be an option, or even possibly AP strings. Both of those would represent less expensive alternatives to the full orchestra strings.