There are a number of Omnisphere functions that are modified by combining a mouse-click (or click and drag) with one of three Key Modifiers; the Command/Control key, Shift key, or the Option/Alt key. In the manual these are referred to as:
Control-Click (Mac users, use Command-click) - Brings up contextual menus.
Sliders & Knobs: resets the slider or knob to a neutral or default position.
Browsers: allows selection of multiple Attributes.
Envelopes (editing): Control-click and drag to engage the Lock function.
Sliders & Knobs: Shift-click and drag allows finer and more precise adjustments to values.
Envelopes (editing): Shift-click and drag to engage the Zoom X/Y function
Option-Click (PC users, use Alt-click)
Envelopes (editing): Option-click to engage the Snap function.
Knobs: Option-click on a parameter to display its value without changing it.
NOTE: Omnisphere defaults to linear mode. Your host may determine a different default mode, but you can still temporarily switch to the alternate mode by using Option-click.