“Sticky” by default is only available for “post” type. When we want to do it for CPT, the common suggestion is to create a new field for that purpose, but that also mean you will have retrospectively add a value to all posts existed before you add the field as well, because of how SQL sort.

To overcome this issue, I figured the most simple way is to enable “Post Attributes” for the CPT that you want to sort. Then you would see “Post Attributes” on the sidebar when you are editing a post from that CPT.

One of the field in this box is “menu order”, simply change the value to 1. And then in the “Listing Grid” widget, first sort by “Menu order” with “Desc”, and then sort by whatever default sort you want next, such as title or date.