Yes, it’s with a normal left click. I see it happens only for the pdf links (please see screenshot). The extension imports the reference for web pages.
Although the extension does not support metadata extraction from pdfs, the development version of JabRef now supports improved detection and extraction of metadata.
You can get the latest version here: index - powered by h5ai v0.29.0 (https://larsjung.de/h5ai/)
Remember to make a backup of your library before trying out the new version