I take it you have imported a video into Camtasia that has subtitles? If true, I don't think Camtasia can do that but there may be a work around. Can you play the video with the VLC media player? You may be able to turn-off sub titles in the VLC playback and then record that playback with Camtasia - creating new video without the subtitles. If you can't turn it off there, then the video was produce using a method that didn't use a separate sub title track which leaves one last chance: Cropping it out.