If you have the tools, you could make the L shaped wood block like Blue eyes. Then if you also need to keep bunny from chewing on the edge of the couch next to the board, keep the wire panel up and secure it to the wood slat to keep the couch blocked off. Or instead of the L block, screw brackets into the drywall securing the fencing to it. If you can't or don't want to screw brackets into the drywall , you could try taping the bottom of the panel to the floor with duct tape. It might just be a temporary solution, but you just need it to work long enough that your bun learns the panel can't be moved anymore and gives up messing with it.
Another option is to also put a tunnel back there for bunny enrichment. This is why your bun wants wants to be back there in the first place. They like small safe crawly spaces. To make a tunnel you can use irrigation piping, cardboard cement forms, or making a tunnel out of pine boards. Though you would still need to block off the top of the tunnel as mentioned above to protect your cords, or put the cords in chew proof protectors.