Yes, you can add a note or description to your non-working hours. It is useful to track later the reason for the non-working hours. For example - Vacation off, etc

Related: How to add non-working hours for my team aka Service Provider(s)?

To add a note, simply click on the calendar and select non-working hours.

Then select non-working hours again and add the note.

To check all your non-working hours and notes, click on Settings > Operating hours, then go to non-working hours