Yes, you can add attendance notes in bulk.
To add a note for the future, the easiest way to do this is to record a planned absence. While doing this, you can select a group of students and the note that should appear in registers at that time. you don't need to add an attendance mark in the planned absence if you don't want to change the mark selected in registers.
You can also add an attendance note by using either of the Bulk Mark options on the Students > Attendance > Bulk Edit Marks pages. You can see how to do this here.