How to change SAGA path in QGIS 2.18 Standalone
I doubt that there is much use trying to change the path to SAGA 3.0 since there are no SAGA 3.0 algorithm descriptions in Processing yet:
(screenshot from qgis-dev on 2016-11-04)
SAGA algorithm parameters keep on changing, most likely it's not as simple as renaming an existing folder of descriptions.
In QGIS 2.18.2 on Windows, SAGA folder option came back again. Yay!
And SAGA 3.0.0 is now up and running.