How can I set up an optional choice filter in Survey123? I have a survey with plant species where a plant family contains multiple genera which have multiple species. If a family is selected, the choices of genera should be limited to genera that occur within this family.
In case the family field is left empty, I want to include all possible genera in the genus-dropdown.
So far, I tried if statements, such as if(${family}=null, genus , selected(${family}, Family)) or alternatives, e.g. using string-length(${family})=0 as condition---however, with little success.
