Add the ability to put notes on grades
Most spreadsheets allow you to add an invisible note to the entry of a cell. The presence of the note is signified by a colored corner. This could be used to explain an entry, show an agreement with the student to update his/her work, so on.
The Aeries Gradebook has had the ability to add notes related to the student and assignment for quite some time. Somewhat recently the ability to manage this from the Scores by Class page was added, directly from the rectangle icon, as this idea described. Custom codes and freetext comments can be used.