How to get captions if you accidentally imported a clip from FCPX
Export an SRT subtitle file and then import that to FCPX
If you imported an FCP clip and wanted to get a captions/titles file know that FCP can only caption/title FCPX projects, not clips.
Importing clips will get you FCP ranges.
The workaround is to export an SRT subtitle file and then import that to FCP via File/Import/Captions menu.