Prefered Delivery time : add custom list items

Hi Team!

this plugin is very useful and well configurable, but i’m here to ask if there is a way to add custom List items into the dropdown “Preferred Delivery Time” at customer checkout page.

I’ll explain myself:

after the Vendor made his delivery configuration, customer will see in checkout page the drop down with all calculated Delivery times.

I need to add a “custom time” called “As soon as possible” or “When Available” (or something similar), in addition to all calculated times.
No calculations are needed for this item, it’s just a simple “label” to be printed into the order, such as other delivery times.

This it’s useful for me because my store can sell food, so in this way a custome can choose “When Available” giving the vendor more time to organize his delivery.

Thank you guys for your good work.