Although Android M isn't slated to highlight a laundry list of major features and changes to system, that doesn't mean that there won't be a large list of changes coming to the system overall. So far within the Android M developer preview there have been a number of different tweaks and changes that point to possible new things to expect within the stock Android version of the operating system, although it is entirely possible that not all the things which have been discovered so far about this upcoming version of Android will end up making it into the final release which is expected to hit later this Fall.
So far, we've seen changes to the share menu as well as configurable quick settings tiles, among other things like the Direct Share API and the new Doze feature aimed at extending battery life for users. It seems Google may be looking to also introduce a new management menu for default apps in Android M, where users will be able to make tiny changes to a small list of default applications that are installed on the device. This is something that would be a first for the stock version of Android but various iterations of it have been present through other non-stock forms of Android before.
For those testing out the Android M developer preview, accessing the default apps menu is fairly simple. Google has placed the default apps menu inside of the apps menu located in settings, and once there, tapping on the three-dot button up in the top right corner will display a panel of options which includes "advanced," and inside advanced the first option is "default apps." The list of apps included seems to be limited to system defaults and not third party downloaded apps gathered from the Play Store, and each application in the list will reportedly have an associated set of options or actions which can be utilized. While most people aren't likely to mess around with this particular option, heavy users of their devices are sure to find this a nice change, especially those who may end up installing other applications which supersede the default system apps for various tasks.