When you need to edit multiple flight entries on the Mac you can batch edit using a shift select and the right column flight details section.
Before you can batch edit flight you will need to make sure they are Unlocked. When you are finished making the batch edits you can Lock your flight again to avoid accidental edits.
Highlight the flights you wish to edit and choose Unlock.
You'll want to organize your flights in an order that will allow you to easily select the flights you would like to edit. As an example, you can sort your flights by Type if you need to edit a field based on the Type of aircraft you were flying.
Next, select the flights you wish to edit using a shift-select (select the first flight you would like to edit, scroll down/up to find the last flight you would like to edit, hold down the shift key and select the last flight).
On the right hand column make your changes and all the selected flights will change.
All your flights will be updated with the entered changes. In this example the simulator time for all of the entries selected which showed as "Multiple Values" was replaced with 0 deleting all of the SIM times with a batch edit.
Also see how to Batch Edit using Auto-Enter.