Set transition defaults
You can set the default transition that is used with the Command-T keyboard shortcut. You can also set the default duration for transitions.
Set the default transition
Click the Transitions button in the toolbar.
Control-click a transition, and choose Make Default from the shortcut menu.
Set the default duration
You set the default duration for transitions in Final Cut Pro preferences.
Choose Final Cut Pro > Preferences, or press Command-Comma (,), and click Editing.
Use the “Duration is x seconds” value slider to set the duration, in seconds, of all transitions you add to the Timeline.
You can adjust the duration of a transition after it is in the Timeline.
Note: Some transitions have a set duration and are not affected by this setting.