When you click “Done, add title to movie” your text will appear in the timeline as an independent clip. You can change its position in the timeline just like any other picture or video clip.
If you want to edit your text after it has been added to the movie, simply double-click on the clip, or else right-click and select “Edit title” from the menu that appears. You will be taken right back to the text tool you just used.
When you are done editing your text, simply click “Done” to return to your Collections.