How to create a png with transparent background in inkscape?
That's actually Inkscape's default.
Open File → Document Properties and click the background colour. Make sure the alpha channel is 0. As so:
Go to File → Export Bitmap (Shift+Ctrl+E) and save a file with a .png extension.
You're done.
Shortcut, at least in MS Windows, is (Shift+Ctrl+E).
Inkscape 0.91