Shift is the vol+/vol- control on the stalk, pushing it in and holding it is reported by the Sony Stalk to the empeg as 'shift',
this means that all stalk buttons can be 'shifted' [except for vol+/vol- which is treated as shift seek+/seek-].

To use shift requires translations be setup but there are 6 extra functions the stalk can do.

BTW: the normal left/right buttons on the front panel work in the menu even when the stalk buttons don't, so you could work around the above bug by mapping the seek+/seek- stalk buttons to from button left or right when the menu is active in hijack without much bother.