Being forced to reach the keyboard every time is cumbersome.
There are a couple of super convenient solutions, especially for those who use a 3d mouse. We only need the approval of the “McNeel” team. 
Method 1:
Use simple “Away gesture” (a.k.a. L-shaped gesture) control to switch between a Dual drag strength mode or Dual snap mode. Here is a detailed explanation of the Dual grad strength mode:
Likewise, the Dual snap mode could use the same principle, the Rhino users just needs to decide which of the two modes they want to set by default.
If you drag the Gumball handle as usual along its own axis, this should be a Smooth dragging by default. However, as soon as you move away the mouse pointer from the Gumball arrow handle (while still holding the left mouse button pressed), that will trigger the Snappy dragging, because Rhino will be smart enough to understand that you want to snap to objects that are away from the arrow handle. No need to press or hold any keys, no need to leave the 3d mouse.
Method 2:
Activate Snappy dragging by dragging the Gumball arrow handle normally and then moving the mouse pointer over the objects of interest where you want to snap, then either (a) make a circle movement there or (b) hold the mouse pointer in the same spot for at least 2-3 seconds (the time period must be user-adjustable in milliseconds, similar to the settings of Smart track). Rhino should be smart enough to understand that when you do one of these two gestures, you want to activate Snap dragging.