Combiner (Pitchbend) is a very simple MIDI-only JSFX script that just combines pitchbends from two different channels into one, by summing them up. Channels 1-8 are the main channels, while 9-16 are the channels that get summed up (combined) with the main channels, but in regards to Pitchbend only — other messages are passed through unchanged. For example, channels 1 and 9 will combine into output channel 1 (that contains the sum of their pitchbends), channels 2 and 10 will combine to output channel 2, and so on. (so only the first 8 channels will have pitchbend outputs)
This can be useful if you already have pitchbend messages but want to fine-tune it manually by combining them into one, if the synth does not support multiple ways to control that behavior.