GarageBand for Mac: Rename MIDI regions in the Piano Roll Editor
You can rename the selected region or regions in the Piano Roll Editor. If you select multiple regions, they are all renamed to the same name, unless the last character is the number “1.” In this case, the regions are renamed in numeric sequence (1, 2, 3, and so on).
Rename selected MIDI regions in the Piano Roll Editor
In the Tracks area, select the regions you want to correct.
Make sure the Region tab is selected in the Piano Roll Editor inspector.
In the Region Name field, select the name, then type a new name.