I usually have both the audio and its transcript available, so generating the English transcription isn’t always necessary. Would it be possible to upload the audio first, followed by the transcript I already have?
No, it’s not possible to skip the transcription step. But what you can do is:
Upload the audio
After transcription has finished, open the text, and in the reader page sidebar, open the Edit tab, and replace the auto-generated transcript with your own and click the “Save” button at the bottom.
This has the advantage that the text-audio synchronization will be maintained, even after replacing the transcript (assuming that there is sufficient similarity between the auto-transcript and your own).