I want to add a single select list custom field in board of Jira that shows a list of Milestones created (already existed and newly created) in the board in order to select single item from that list through an automation.
Problem: Whenever a task or issue is created, I want a single select list custom field that displays all the Milestones in the board in order to select one from the list to associate it with the task or issue created
Steps Taken:
1- I have made a single select list custom field (Milestone) and included "select an option" in the option field while creating and associated it with the screens

2- I made automation with the following rule



3- Now whenever I create a task, list of milestones is not visible to me (can be seen on the bottom-right side of the screen shot at 4th position from bottom). It is not populating the milestones from board, instead it is showing the option which I put in this custom field during the time of creation.

Kindly help me to resolve this issue.