Sounds like a specialized productivity tool would be of little help there, since no tasklist can withstand the problem of just not being able to get started on a task. And something like GTD is only going to be another burdensome and anxiety-inducing task for someone with executive dysfunction.
A simple but constant reminder system (perhaps with a smartwatch or phone) can be of more use.
Organizational tools can help with #2, and can also help break down tasks to be less daunting, which can help sometimes help #1, but only if the executive disfunction is being managed with other means like medication.
And then if you use a system malleable enough to reduce starting effort to 0 across anything (project or task) you do... you just about solve that problem
How can a productivity system reduce the starting effort of any task to zero? There’s such a thing as activation energy.
Sure, you can try breaking a task down to its smallest component, but not all problems can chunk like that. And even the smallest component will take non-zero work.
I would be curious to learn about a system that could actually accomplish that.