2. <jargon> (To make) a small or insignificant change. E.g. twiddling a program often fixes one bug and generates several new ones (see also shotgun debugging).
Bits are often twiddled.
Twiddling a switch or knob implies much less sense of purpose than toggling or tweaking it; see frobnicate.
Bit twiddling connotes aimlessness, and at best doesn't specify what you're doing to the bit; to "toggle a bit" has a more specific meaning.