It would be a nice feature if you where able to make your own marks in an analysed match. This could be done in a number of ways. E.g. you could have a drop down menu where you could define your mark, and maybe add a comment to it. Another solution (not as good, but easy to implement) could be just to mark moves with a comment added to it.

In this way you could mark errors that you do not understand. Errors where you overlooked the right move. You could also define marks for specific types of errors (holdinggame errors, backgame errors ...). Then later on you will have a quick way to find the interesting parts of an old saved match.