Board Thread:The Quarters - Q & A/@comment-24548070-20140215075807/@comment-24150802-20140221174752

There's no way within the website or mobile apps, but you can use the API to adjust any attribute of any task (including a todo's value) but you need to be careful to not accidentally make incorrect changes. The API makes it possible to make very large changes to your account, including completely destroying it.

However adjusting a value like this falls outside of HabitRPG's normal usage. Can I ask why you would like to change a task's value? There might be some other way of achieving whatever you had in mind.