Partial screenshots feature found hiding in Android 7.1 Nougat
The function is present, but hidden, as in a small change in the Android source code is required to enable it. It is unclear if Google or other Android smartphone manufacturers will be enabling the feature in their Android 7.1 Nougat builds, but it will present a welcome change which will make taking screenshots a more convenient experience.
The functionality, enabled by third-party changes to the Android source code, can be seen briefly demonstrated in the video below.
source: XDA Developers