Nudge Region/Event Length Right by Bar

Extend the length of the region or event by a bar. The length of the extension depends on the time signature.

Only MIDI regions can be extended using this command. Applying it to an audio region does nothing, not even flash the “can’t do that” indicator.

The “Nudge Length” commands are not specifically mentioned in the documentation for resizing regions.

Resize regions in the Logic Pro Tracks area — Apple Support

You can shorten both audio and MIDI regions so that only part of the region plays. You can lengthen MIDI regions to add silence to the beginning or end of the region. In addition, you can resize the common edge of two adjacent regions to control the transition between them and remove overlaps.