You could simply do this (you can put this in the initializer script):
@BaseScript FieldBehaviours fieldBehaviours
FormField ffPruebaSL = getFieldById("customfield_10201") // Change with your field ID
// If you want the "None" Option to be available uncomment the following line and comment the previous one
Jira is a great tool to use across different departments. Forget that paperwork – switch to Jira and get that tasks done smoothly. Marketing Jira allows for a complete digital transformation of you...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events