Undo button in toolbar for Windows touch devices like Lenovo Yoga C740

I've recently bought a Lenovo Yoga and I'm pretty happy so far. There's only one problem in Photoshop: I can't find an easy way to press Undo when the device is in tablet mode

I know you can scroll through the history with a three finger touch - but that isn't practical when you want to quickly draw and undo a line until it has just the right curve.

Other than that you can only go via the top menu - which takes two clicks, so that's super annoying..

I've found out how to display keyboard functions like strg, alt and shift in the toolbar but it doesn't seem like there is an option to also add sth like Undo to it even though it would be the perfect solution. You could draw with your right and hit undo with your left thumb.

All my research didn' find anything useful either. Am I just missing something or did Adobe really not think that far yet ?

Thanks for your help in advance,

Larissa