The tasks seem endless. A mountain of details to be combed through one by one. Wishing things done, does not work. Only the application of some form of book keeping has a chance. A list or a table of what one is testing and the results of the test. Updatable would be a good feature too.
Sometimes one needs assistance with testing that all the changes work right and that things that were not fixed, are themselves still working. With software there is always the possibility of side-effects. It is a wonder that it ever worked before the fixes as one applies their own philosophies to the legacy code.
Often the effort is invisible. Sometimes it can be measured in size. Other times it is shown in performance. If nothing else, it is reflected in the ease a new feature is seamlessly integrated with what was essentially a different POV. But I have no more time to ponder for there is so much to do!