The last individual Edit can be undone one at a time with the CMD Z (Mac) / Ctrl Z (Windows) keys.

To restore immediately the pitch and time values before editing started, LEFT CLICK a Block or Range you wish to return to its original values to select it. Then, RIGHT CLICK it to bring up the menu shown below and select Modify Values and then Reset Selected Values

Warp - Modify Values

The selected values will snap back to their Original measurements and positions.