Thanks for that pointer, Brian! I've never used the KWIC feature before; like Morten, I couldn't see the point. But now I'll want to keep alert for possibilities for using it effectively. For instance, using the techniques that the tutorial suggested, but searching for εἰς and setting the Left word setting to 2, I quickly found that the most common words immediately preceding εἰς in the NT (apart from pronouns, conjunctions, and definite articles) are forms of ἔρχομαι and πορεύομαι, not surprisingly, but also πιστεύω (perhaps also not surprisingly). Good stuff! This really is a tool with high potential.
Morten, regarding your wish, it's actually pretty easy to type in a search range in the KWIC tool. For instance, in the preceding example, reducing the range from Matt-Rev to Matt-John still retains a significant presence of πιστεύω, but reducing it to Matt-Luke almost completely eliminates πιστεύω (just Matt 18:6 // Mark 9:42). By contrast, specifying a range of John; 1John-3John promotes πιστεύω to the very top of the list, ahead of ἔρχομαι!
And BTW, Brian, the main BW Classroom Tips page just went into my Ermie!