How this maps to GTD
Capture. One box for everything, so you stop using your head as a storage device. The capture field at the top writes straight to the inbox and asks no questions.
Clarify. Each inbox item gets one decision. Is it actionable? If not it is reference or it is deleted. If it is, and it takes more than one step, it is a project, and the project needs a next action written as a physical thing you could start now.
Organize. The lists here are the standard ones: next actions, projects, waiting for, scheduled, someday, reference. The point is not the names. The point is that you can find everything you deferred without rereading it all.
Reflect. The weekly review is the part people skip, and skipping it is what makes the system quietly stop being trustworthy. The stepper walks the lists in order so it takes 20 minutes instead of an afternoon.
Engage. Pick from the next actions list and work. If you want a timer around that, the pomodoro timer takes a task id from the Focus button on any next action.