How do I create expression maps for Kontakt instruments which have dedicated .nki files for different articulations?
Welcome to the forum @swastikroy03.
I think the solution to your problem will be to add Channel Changes to your various Playback Techniques.
E.G. if channel 1 is Arco and channel 2 is Pizz, for your Natural and Arco Playback Techniques you’d have an Absolute Channel Change to 1. Vice versa for Pizz.
I have the same thing set up for Clean and Distorted Guitar.
Relative Channel Changes work the same way but you don’t specify to play “Channel 2”, you’d use 1 to advance the channel by one.
This is useful when you have multiple instruments that might have the same nki setup (e.g. all the strings may have Arco then Pizz then Tremolo, in that order). You begin on different channels but with same organisation of technique, the one Expression Map will work for them all.