Thank you!
Sorry, that's not possible in the version you're playing, but I've already implemented an alternative way to rotate items, right click and middle click, by using the WASD keys, the left alt key and the left shift key respectively for the next version.
Though I suppose I could update the current demo with this addition... There is a chance you won't be able to transfer your save file to the updated version though, but if that's ok with you, I'll do it!