Show/Hide Gain Reduction Meter
Shows or hides the Gain Reduction meter that appears at the top of the channel strips. The meter is only actively used by built-in Logic plug-ins. Gives a quick view of the amount of gain reduction being applied.
Channel strip controls in Logic Pro – Apple Support
Each channel strip has a set of controls (also called components), which varies according to channel strip type. You can adjust the channel strip volume and pan position, mute and solo channel strips, add and adjust effects, and send the output to auxiliary or output channel strips.