A "Rotate board" button is now available from the Options -> Toolbar menu that can be added to your main toolbar (v5.1.2.84)

[whelanh]

In order to rotate the board perspective from White to Black or vice-versa, currently you go to the three bar menu at the lower left of the chess board and select "Rotate board". Now you can choose to add a "Rotate board" button directly in your main toolbar so you can do this with one mouse click instead of two.