Short answer: macOS has no setting that stops Notification Center hiding notifications behind "4 more notifications". Still Dock adds one: the Show every notification switch keeps the whole list open every time Notification Center opens.
The switch is in the direct download of Still Dock, as one of the paid locks. The Mac App Store version does not have the switch.
Open Notification Center from the clock in the menu bar. macOS shows the 3 newest notifications as cards. Every notification beyond those 3 is folded into a single button that reads "4 more notifications" (the number is how many are hidden). Press the button and the hidden notifications appear. Close Notification Center and open Notification Center again, and the list is folded again.
Grouping is a per-app setting in System Settings, under Notifications. Grouping decides whether several notifications from one app stack together. The 3 card limit sits above grouping: with grouping set to Off for an app, macOS still shows only 3 cards and folds the rest behind the button. This was tested on macOS 27.0.1 with a test app that sent 8 notifications.
Turn the switch off at any time and Notification Center goes back to folding after 3.
Still Dock finds the "more notifications" button by its accessibility identifier and presses the button, once each time Notification Center opens. Still Dock never reads the text of a notification and changes no notification setting in System Settings. The only thing counted is how often the switch is turned on or off, as an anonymous usage count that you can turn off.
Not with a setting. macOS has no switch for the 3 card limit, and grouping off does not change the limit. The only way without an app is pressing "4 more notifications" each time Notification Center opens.
No. The switch is in the direct download of Still Dock only, because the switch needs the Accessibility permission, which the Mac App Store sandbox does not allow for this.
Yes. The switch is one of the paid locks. The size lock is the only lock that comes with every download.
Not yet. The switch is on the Mac. A row for the switch on the Still Dock iPhone app is planned.
The switch was built and tested on macOS 27.0.1. Notification Center changes between macOS versions, so a future update from Apple can need an update from Still Dock.
Looking for the other locks? Ways to lock the Mac Dock covers the Dock itself, and how to disable Cmd Q covers quitting apps by accident.