Thanks both for the inputs. Frankly, the ticket has been parked for almost 3 years and I am not quite interested to fly this ticket any more (plus the cost of positioning from the States to BUD is quite high these days). When I called DL last night, I was trying to refund the ticket if the agent told me I should fly before 12/31/2022, which I was informed back in Mar. 2020. Now that she assured me I can still fly by 12/31/2023, I will just leave it "parked" until next summer, in case I want to travel to Europe by then.
Another reason I decided to postpone canceling/refunding this ticket is because the exchange rate of HUF/USD is 20% lower than Mar. 2020, which means if I refund the ticket now, I will lose 20% what I have paid when purchased this ticket. Anyhow, the DL agent told me as long as this ticket is a refundable fare (which it is indeed), I can ask for a refund any time when I opt to do so.