Google Scholar has made some changes and no longer allows us to input extension buttons on their page.
However, we have developed a solution that will work on every website that the extension works on and while this change only effects Google Scholar you can use the following workflow on any website.
Search on Google Scholar as you normally would - as you can see, there are no extension buttons available next to article titles (as there are on other websites where the extension inputs buttons):
However, the extension icon (Papers logo) next to your search bar now displays numbers - clicking on the icon displays a dropdown list of all articles available on the page. The extension shows the information if an article is already in your library and the option to view the full text (by clicking on View PDF) if the article is an open access one or already part of your library.
You can also select multiple articles at the same time to import all of them to your library by checking the small box next to each of the article titles and then clicking the "Add to library" button in the bottom right corner:
The "Select All" button at the bottom will import all search results from the page directly to your library.
(updated July 11th, 2023)