There is a whole world of bugginess going on with Cursor Shift Variants & Relative Construction Methods over several versions of AC.
In AC13 the CSVs can be activated by just using Shift to constrain the cursor, although you can only access them through the Control Box palette.
In AC14 they introduced separate buttons for those who customize their work environment. Unfortunately, these new buttons will only work when using Shift if you have the Control box open! If you select a Relative Construction Method beforehand then the CSVs work form both the Control box and toolbar buttons.
Now in AC15, the Cursor Shift Variants will only work if you select a Relative Construction Method beforehand. If you don't, the CSVs won't work at all from either the Control Box or toolbar buttons!
Their functions can be replicated by using the guidelines, so is it time the CSVs and duplicated RCMs were retired? (two less things to debug?)
The only one I'd keep would be the Special Snap Constraint (the Boingy-Boingy tool!
) to quickly find a point halfway between two other arbitrary points.