When history of notifications is enabled, there is a list shown in the click-to-show window of Notifications. However, this list should not be shown in the new notification window for current event in my opinion. I am not sure I used the correct terms for the description, so I am going to describe it in detail. When a new even coming, there is a notification pop up window notifying user of the new event. This window is not the one that shows when user clicks the Notifications tray icon. Therefore, this window should only show the information for the currently incoming event but not the list of events stored/enabled in the click-to-show window of the Notifications. In other words, the option of keep a history of notifications should not affect the behaviour of notification popups but only the click-to-show window of the Notifications.
I don't undertand, how would the history affect the popup? Or do you mean if you get multiple notifications from the same application in a row that it groups them together into one popup?
My observation is related to kde-connect. When the phone is connected and receiving messages, for example from one single contact, the popup window of notifications showing the second message along with the first message if the first message has not been read. Of course the messages are grouped in click-to-show window of Notification. This is reasonable.
Not sure we'll be able to accommodate this proposal, sorry.