Open the target selling period rule
Open the "Before selling period" or "After selling period" section
Enter your message in the "Alert message" input field
Save
If the input field is left empty, the following default messages are displayed automatically:
Before selling period: "Selling period has not started yet."
After selling period: "Selling period has ended."
Note: Alert messages support plain text only. Text formatting such as bold and links, and variable insertion are not supported.