Android's notification system has gone through some pretty intense work since the start of the platform, but that doesn't mean that third-party developers can't improve it even more. Case in point: Floatify, a customization app that's been floating around (sorry) for the better part of two years. The latest version is number ten, and it adds a couple of features from the new Android N Developer Preview. If your device isn't invited to play with the Nexus crowd (or you just don't want to deal with the instability), you can back-port some of those neat touches.
First of all, the update adds an Android N theme for its custom notifications, in both dark and light flavors. You can access them both in the "style" section of the app. Second, the notifications now have access to a "swipe action menu," which mirrors the long-press or slide/swipe actions (depending on the actions you want to achieve). These options should change with each app, but they're fairly obvious: messenger notifications can be replied to in a pop-up window or sent to the app itself.