Create a midpoint with two new points (created by the tool itself) Undo the operation. The undo operation should not require 3 steps to undo everything that has just been created. From a user point of view, this is just one operation. It should be canceled with one click.
Fixed with the creation of object groups, will be available starting from 4.9 http://commits.kde.org/kig/229e459186a1363c634e4b5c9e46a9ce64e864e5