Does anyone have any suggestions on how to connect two washing machines to a single standpipe drain without having to manually pull one drain hose out, and putting in the other each time?

Both machines will not be running at the same time (this is for a two-family house) so I don't have to worry about both discharging gray water at the same time.

Does anyone have any suggestions on how to connect two washing machines to a single standpipe drain without having to manually pull one drain hose out, and putting in the other each time?

Both machines will not be running at the same time (this is for a two-family house) so I don't have to worry about both discharging gray water at the same time.
What I'm understanding is both units are in the same room. If you know someone handy with copper fittings and can soldier... you can "Y" the two drain lines together and have sufficient vertical pipe to place in the drain so it doesn't come out.

Make sure the pipe is firmly fitted into the drain hose and clamped.

It would be great to send you a picture... however that doe not appear to be an option.