User in the custom field
User in the custom field : Only user(s) in the given custom field can execute the transition
(1) Click 'Add condition'
(2) Select User in the custom field and click Add
(3) Select the custom user field
(4) When added successfully, you can see 'Only user(s) in the Multiple Users Picker custom field can execute the transition' showing in the condition list
(5) Users who are not in the custom field will not see the transition button