'Is Featured Discussion' column is a hidden site column and is grouped in "Custom Columns".
You can access the hidden site column via accessing a custom site column under "Custom Columns" group, then copying the URL of the custom site column, its URL should be like:
https://your site/_layouts/15/fldedit.aspx?field=customSiteColumn&Source=yoursitename2%2F%5Flayouts%2F15%2Fmngfield%2Easpx%3FFilter%3DCustom%2520Columns
Then change the field paramter of the url to IsFeatured, you will see the column setting page:

Per my knowledge, you are unable to re-use it in other lists except Discussions as the column is hidden and there is no way to change it.