presta
Guru
This popped into my YouTube feed.
I presume it has safety implications as the door area would be very weak.
View: https://youtu.be/AAtkoje4-eM?si=hqOGXfXc_6gkt3Gl
It's not new, the BMW Z1 has doors that retract into the sill:
View: https://www.youtube.com/shorts/oxlQv4xt20k