REPL, hot code reloading, test code that gets me into the debugging state. Really to dev well, u need to spend considerable effort getting everything setup to maximize flow. Having and not having flow can be 20:1
Our concentration is fickle, so streamlining is key.
You need to write stuff down, use it as a guidelines to stay on track (hardest part), and tick it off. Everything else is waste of time that masquerades as "productivity hacks."
The goal is to outsource your list of things to do because you have a fallible memory, but the biggest goal is doing something that drives your life forward. Don't get stuck looking for the new productivity fad or rewriting your todo cli.