You can set the origination point of some title styles. To see if this setting is available for a title style, click the preview monitor. If the pointer changes to a cross-hair, you can click a place in the preview monitor where you want the title to begin.
In other words, iMovie 4 lets you drag certain title styles to change their position in the window.
Some tests revealed these title styles are draggable:
1. Bounce Across
4. Cross Through
7. Video Terminal
Best I could tell, it's only possible to drag a title up/down, never left/right.
The note about the cross-hair cursor isn't quite correct. Some draggable titles never display the cross-hair cursor, while some that display the cursor aren't draggable.