Can I add custom notes for a time entry?
Yes, you can, either when starting a task in an external web app or when working on an internal one in TMetric. The note you add to a time entry from outside can be also viewed and edited in the desktop client and web application.
Custom notes can be only added to a time entry, which is related to a task (internal or external). They are stored in the Description field and can be changed in the time entry editor window.
The name of the task can be seen in the bottom right section of the editor window. And, it does not change, when the custom notes are being added to the task.