Is possible to use Milestone as summary task on GitLab community Edition?

I need to confirm if the Milestone functionality can be used to summarize lower level work item dates, % Complete and effort.
Thanks in advance.

Not sure. You have to provide more explicit requirements.
Milestone/issues can be used to keep track of work items in a simple kanban board style. Community version doesn’t have subtasks to do full scrum.
Following page may provide with more details.