Per the title and after some personal experience, it can be quite cumbersome to begin reading an article then attempting to add a bookmarklet only to realize that the domain is not in the list. This breaks the users overall flow and causes them to need to open the sidebar and manually add the domain.
High-level solution would something like:
reading an article on medium.freecodecamp.org, which is not in the domain list.
user selects the text and presses B to add the bookmarklet
medium.freecodecamp.org domain is added to local storage, then the page is refreshed, which then allows the bookmarklet to be added like normal
cedricium
commented
6 years ago 
Per the title and after some personal experience, it can be quite cumbersome to begin reading an article then attempting to add a bookmarklet only to realize that the domain is not in the list. This breaks the users overall flow and causes them to need to open the sidebar and manually add the domain.
High-level solution would something like:
medium.freecodecamp.org, which is not in the domain list.medium.freecodecamp.orgdomain is added to local storage, then the page is refreshed, which then allows the bookmarklet to be added like normal