Screenshot of the Mastodon web interface showing how to enable the new experimental grouped notifications feature. To enable it, navigate to “Notifications” in the main menu, then open the settings using the cog icon in the title bar, then enable the feature under “Experimental features”.
https://media.oisaur.com/media_attachments/files/112/812/306/233/652/442/original/dcacd4802dad6400.png