At the moment the main workflow assumes you don't have transcriptions, and that you are using the app to generate those as well as to correct them if needed.
However there is an advanced workaround to add existing transcriptions if you have those. Eg when working off scripted material that is read out loud by a presenter or etc..
Select all of the text of the transcript, delete it and replace it with the text of the transcript you already have.
Then click the alignment button 🔄 and the app will re-align the text you provided with timecodes.
6. You should then add speaker labels, and review the paragraph breaks 🤞