Some records might have damages in one stereo channel only. If those damages are difficult to repair you might consider to simply copy the undamaged channel over the damaged channel. You'll lose the stereo effect in the process, but the result might still sound better than trying to deal with the damage and modify or destroy the music in the damaged channel, special when the damaged area is not very long.

1. Open the track menu (triangle arrow on the left side of the track, or SHIFT-M on a selected track) and select Split Stereo Track, which splits the stereo track into 2 tracks
2. Identify the start and end position of the damage, then select the same position in the undamaged track (shows as white background after selection), then hit CTRL-C to copy into the clipboard
3. Take a note of the selected area at the bottom of the Audacity window
4. Now select the identical length within the other (damaged) track
   1. select the start position close to the required position, then move the start position with the left and right arrow keys, until the selection start matches exactly (in this example this would be 20:37.443)
   2. press and hold SHIFT, then move the right arrow key to the exact position of the selection end (e.g.