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.
A few other cosmetic options, updated translations, and support for Go Locker are also included in the update. Floatify remains free in the Play Store, and the Pro Unlock for deeper customization options is $3.