If you have an activity that you recorded by mistake and you don't want to have the recording in Jiminny then you can delete it.
Just visit the playback page, click Settings on the top right corner and Delete (bin icon).
Remember, this will remove the activity permanently, including the recordings and will not be recoverable!
If you don't see the delete option then it has been restricted by your Jiminny Admin. Reach out to them and they can delete the recording.