Change the gain of audio regions in Logic Pro for Mac - Apple Support

You can change the gain of audio regions with the Gain tool, or in the region or cell inspector.

Use the I/O Labels window in Logic Pro for Mac - Apple Support

Edit in the Audio File Editor in Logic Pro for Mac - Apple Support

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Gain plug-in in Logic Pro for Mac - Apple Support

Audio Editor - Apple Support (MN)

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Gain plug-in in Logic Pro for iPad - Apple Support

Logic Pro for Mac Project Audio Browser interface - Apple Support (AE)