This question is really two questions wearing one sentence: does fluid accumulate (swelling by evening) and does it still drain (normal by morning). Together they place you on the venous timeline.
Evening swelling with a morning reset is the signature of early venous insufficiency: valves losing ground against gravity through the day, with a night of lying flat still enough to drain the backlog. Sock marks that fade by breakfast tell the same story. It's common, manageable — and the right moment to act, because compression, movement and elevation work best at exactly this stage.
Swelling that stops resetting is the signal the system is falling behind: fluid sitting overnight begins the slower changes — skin discolouration, thickening — that are much harder to walk back, and persistent swelling raises the lymphatic question too. In our community's stories, "it used to be gone by morning and then one month it wasn't" is the line where "tired legs" became a condition.
Whatever you answered: the pattern is worth two weeks of casual tracking — evening severity, morning state, sock marks. That little diary plus a standing duplex ultrasound request is the entire sensible first response.