Redmine offers integration of Checklists plugin with Agile plugin. It means you are able to view and modify your checklists from the Agile board.
In order to use this feature, please make sure you have the Checklists plugin installed and activated first. Then, go to the Agile board of your project and check the Checklist within Options.
After you do it and click Apply, you should see all checklists you have in your issues of this board.
Now, you can mark checklist items as done or undone from the Agile board.