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Your LimeSurvey version: Version 5.4.9+221101
Own server or LimeSurvey hosting: own server
Survey theme/template: fruity
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I have a ranked question with a bunch of options, one of which is "other.."  if the participant uses this as any of their choices, I want to show an additional large-text question allowing them to elaborate. 

What I'm struggling with is how to set up the condition for this field. I can of course do (pseudocode): "if rank1 == other || rank2 == other || rank3" but that gets old fast if you have a lot of options. Is there a way to simply do something like: "q1.selectedOptions.contains(other)" ?

I can't find anything like this in the manual. 

You only have to count the appearance of "Other" and display the question if the count is greater than 0.
Use function "countif" like
countif("98",that.Q1)
with
98 = code of "Other"
Q1: Code of rank question

 

Thanks. That works.