Multi Level Cascade Select field is not officially supported by Adaptavist ScriptRunner plugin and its component yet.
Pro tips:
Avoid yellow spaces: When you copy/paste the code below, please make sure to get rid of the yellow spaces (shown in this picture). They will raise a “Type checking error” in your console.
How to get option’s IDs: To get to know the custom field and the option’s IDs, in the custom field context configuration screen click on Edit Options and Export CustomFields.
This is a sample JSON file containing the information you are looking for: