Crop Loop ⌥⇧⌘X – Logic Pro keyboard command of the day

  Crop Loop  ⌥⇧⌘X

I have yet to venture into using the Sampler to create samples. Sort of started out as a ROMpler person.

Use the Sampler Zone pane – Apple Support

Crop Loop: Crops (cuts) the portion(s) of the sample outside the loop start and end markers.