Hi all,
This functionality to undo a status change (missed or completed appointments) is a need for us and has been requested by users in the field. The use case that has been articulated to justify this need is often manual errors. This happens more often than thought and the users feel the need to undo their actions (especially around missed or completed status change).
In general, making actions reversible is offering users a way to backtrack from erroneous entries. The ability for users to backtrack whatever they are doing allows users to explore the product without the constant fear of failure. On the other hand, if users have to be watchful with every action they take, it leads to a slower use of the application and nerve-racking experience that no one wants.