Separating your trips back to the original shorter trips is as simple as tapping on an icon.
Step 1: Find the trip you would like to unmerge. Tap on the link icon next to the trashcan icon at the bottom of the trip card.
Step 2: You will see the full map of the merged trips. At the bottom of the screen tap on "Delete or Unmerge".
Step 3: Select "Unmerge" from the list and all the trips will be separated.