Certain categories are automated, in that Life Cycle figures out depending on other factors than just location, that your're commuting, moving about, sleeping and so on. These automated categories would create ripples in many directions if full on edit was possible, and as a consequence, we've locked them for now, to avoid the potentially bigger problem that would arise if full on edit was possible now.
But we know this is not an ideal situation, and our ambition is to allow users to be able to full on edit all categories. We are working on a solution.
Our first steps to this goal has been to change Transport to any category of your choice, and allow full on edit of existing sleep data. Our end goal is full on edit of all activities, no matter their category or relevance in automation.