I know one should be able to remove the square drain plugs in transaxles with a square plug socket/wrench, open ended wrench or a 12 point wrench. What can you do when you don't have a plug socket/wrench? When the open end or 12 point box end wants to round off the plug because it has been stuck in there for decades or previous removal it was given all the torques to re-install.
That's when you think out of the box. Here is my favorite method to get those stuck plugs. Good thing most of these plugs are either 1/2 or 3/8 square.
If you have those hex head sockets there is hope. I even have a plan B if you do not.
Put the rachet side of the socket over the plug. This case is a 3/8 hex head.
Then use a standard socket, in this case size 3/8 socket, and loosen the plug.
If you have one of those couplers to screw two threaded rods together, you can use one of those. Get the socket the size of the coupler, again use that socket and cover the plug with the ratchet side of the socket. Insert the coupler and then use another socket or wrench on the other side to unscrew the plug! Same idea as above!
No coupler, you can use a double nut bolt in place.
Hope this helps you with your stuck plugs!