You can append any Loop through the Edit functionality! After navigating to the Edit page for your existing Loop, click the "+ Add interview" button to add another interview as seen below.
A pop-up will appear for you to add an interviewer for the panel, as well as the option to select an interview type.
Before clicking "Add Interview" to confirm all changes, feel free to edit the calendar invite description. A full run through is included below!
Note: The option to "Add Zoom meeting" will only appear after an interviewer has been selected. That option as well as the option to "Add Zoom Room meeting" will only gather data relevant for the new interview. If you need to change the Zoom details completely, you will need to fully reschedule the loop.