From the exercise page, tap on the 3 dots at the top right, then on Manage Data. Scroll down and tap on EXERCISE (EXERCISE LOGS, GPS TRACKING), and then on REVIEW YOUR DATA. From here, you should see the old exercise page and edit your details as you used to ...
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Credit to @auser23 for discovering this.
Edit: This capability is most likely available in all V4.xx versions.
Thank you for sharing this. I have been trying to figure out how to get seconds back on my workout times. Why would they remove that from the main workout view? Very frustrating that I have to dig that deep to find such a basic stat