When updating a cue where specific channels are recorded into cue parts, a softkey that will preserve the parts that the channels are in. So for example, say I have 5 lights that I want to fade up in a specific way so I record each fixture into it's own part with timings and such. Now I want those same 5 to fade back out, I currently have to update each part individually. Using update preserve parts would allow me to take those 5 lights out and update the cue keeping the five fixtures in the correct part.
