Because Thanksgiving is not actually a liturgical holiday, and doesn't appear as such in Lutheran Service Book, we do not have it on the calendar by default in Lutheran Service Builder. Doing so would create some issues—Canadians celebrate Thanksgiving on a completely different day, and many churches have their service on the evening before Thanksgiving. But "Day of Thanksgiving" is the liturgy that is commonly used for Thanksgiving, and after clicking on the day you want to use it on the calendar, you can select "Day of Thanksgiving" from the "Holiday" dropdown when creating the service. The Propers for Day of Thanksgiving are included in Lutheran Service Builder as shown in the animated graphic below.
