When going in a portal in creative, it is possible to destroy the portal block and still go in the nether, when going back, a new portal is created. This is also possible to do in survival by using a dispenser with a water bucket right in front of the portal and a preesure plate next to it, the run jumping in the portal
Related issues
duplicates
Comments
Forward-resolving as duplicate of MC-175067.
This should most likely be forward resolved into MC-175067, as that ticket is confirmed (community consensus) and includes more information on the issue