Reorganize notification summary

As useful as the notification summary is, I think it needs some improvement.

First: often, after clicking on a notification, instead of disappearing it magically reappears in the summary.

Another problem concerns the display of notifications and their content: for example, with Telegram I happen to see duplicate content of a notification. It would be preferable to see at least the last two notifications in chronological order relating to the chat, as if it were a classic Android-style notification, viewable in full (or almost) without necessarily opening the app.