I don't know if the title is correct but I'll try to explain my question below.
I have created a custom post type "Projects" and the trick is that one project have to be unique and displayed on home page.
I was thinking about adding a checkbox in post edit page and if it's checked post ID will be saved somewhere (I dont know where and how, so please help). In case that another post is checked as unique, old value will be overwritten, so only one post will always be active (unique).
My question is where to save this kind of data as I don't want to create a custom table (if not necessary), and saving in post meta is not suitable for this use case. And also how to retrieve this data form wp DB?