Samsung seems to be working towards rolling out the Android Pie version for its flagship phones which are the Galaxy S9 and Galaxy S9 Plus by early 2019.
According to the report by XDA Developers, in the leaked update of Android Pie beta for Samsung Galaxy Note 9 and Galaxy S9, Samsung is seen to have added the option of floating keyboard feature to the existing built-in keyboard.
As per the report, floating keyboards aren't new to Samsung. It was introduced a while ago with Samsung Galaxy S5 which was running on Android 4.4 but was taken down after.
The floating keyboard can be moved all around the screen which can be seen to be useful with huge display phone sizes like 6.4-inches and so on, but Samsung S5 isn't essentially a huge display phone so didn't necessarily need a floating keyboard.
The floating keyboard enables the phone to be used via a single hand and seeing how the screen sizes growing with every new phone launch like the upcoming Samsung Galaxy S10 Plus is said to be equipped with a 6.44-inches display, it would be nice to have a floating keyboard.
The report mentions how a lot of touchable areas have been placed downwards in comparison to the Android Oreo-based Samsung Experience 9.
This seems similar to floating keyboard that Google added to Gboard a few days back. It brings out a keyboard window which can be moved anywhere on the screen and the floating keyboard mode can be activated from the expanded menu in the top left corner of the keyboard. Also, you can resize the keyboard as mentioned in XDA Developers.