Inventory left click does not work with Touchscreen Mode off but does when it is turned on. However, if Touchscreen Mode is turned on, shift-clicking does not work, it only works when it is off.
[Basically, if TS is on left click works but then shift-clicking doesn't. If TS is off left click doesn't work and shift-click does.]
EDIT: shift double click also does not work for me either way, with TS on or off.