In order to set a certain pre-order availability period for a specific product or for several at once:
Select the products or product variants you need to set up your period for.
Check the box "Enable schedule" in the pre-order settings block.
Choose the start day for pre-orders and click on it in the calendar.
In order to set an end date for pre-orders, choose this day and click on it in the calendar.
Click "Save".
If you want to disable the pre-order period for one selected product or several of them: