The phrase epic has connotations. Epics are embarked on until they are completed. They require heroics. People don’t suspend one epic in order to start another. An epic is only successful at its end.
Our agile planning should be more fluid and less valiant. We should be prepared to change course. We should pick our battles carefully. At every stage we should pick the story that delivers the best return on investment. We should seek to deliver value every day, not just at the end of a piece of work.
By all means break a story into tasks. Please do categorise stories by theme if it helps. But be wary of embarking on an epic.