Undo
Every change saves at once, and most can be taken back.
Undo
Press ⌘ + Z to undo the last action. Press it again to go further back. ⇧ + ⌘ + Z brings it back. On Windows it is Ctrl+Z, and Ctrl+Y brings it back.
Edits in the track card are undone the same way. Text you typed or pasted in a field goes away with one ⌘ + Z.
While you are typing in a field, ⌘ + Z first takes back your typing. When there is nothing left to take back there, it undoes the action before.
After moving or deleting many tracks, an Undo card appears for a few seconds, with the time left on it. Click it to take the action back. The card waits while your pointer is on it.