If you have ADHD, the task itself is rarely the problem. You can do the thing. The problem is the gap: you send the email, you have the call, you tell someone you will circle back, and then it leaves your head completely. Out of sight really is out of mind. Two weeks later the customer asks where things stand and you realize the ball was in your court the whole time.
This is not a discipline issue. It is how an interest-and-urgency-driven attention system works. A follow-up has no deadline and no immediate signal, so it never competes for your attention until it becomes a fire.
Why reminders and folders are not enough
Most tools ask you to remember to check them. A folder of open threads only works if you open the folder. A reminder helps, but only if you set one, and setting a reminder for every loose end is its own kind of overhead that you will abandon by Thursday.
What actually works is flipping the burden. Instead of you remembering to look, the system reaches out and puts the thing back in front of you when it is time. You should be able to say "bring this back to me in three days" in one tap and then forget it on purpose, trusting it will return.
A follow-up system that does the remembering for you
The pieces that make this work are simple. Capture the thread the moment it happens, attach who it is with and what it is about so future-you has context, and set a quiet resurfacing date rather than a hard deadline. When that date arrives, the item shows up at the top of your day, not buried in a list.
The point is to externalize the memory entirely. You are not trying to hold the thread in your head until Thursday. You are handing it to something that will hand it back on Thursday, with the context you will have lost by then.
ADHD Notes is built around exactly this loop: capture in a second, add the customer and the people, and tell it when to bring the thread back. See how it works.