For those of us that use Samsung (I'm using a Tab Note 10.1 2014), it will be handy to have multiwindows support in SD, in order to be able to display another app on the screen, such as a note taking app (that is able to process Spen input) or instruments from other applications.
It seems that multiwindows is easy to implement, needing only a provision in the app manifest file.

I second this!!
Multiwindow support would be very useful. I also have this tablet, Samsung Note 10.1 2014 edition. For several good reasons I always run the app Locus (check out that fantastic app!) at the same time as SD and multi task between them. Locus has multiwindow support. So instead of having to switch between those two apps, I could have them side by side. Or the 2nd window could run a note taking app as mentioned.

So, yes, please put this on your to-do list.