Run a stepper from 2 DM542 drive

[A_Camera]

Sorry to be a pain. I have 4 inputs which need to be changed between. You said I will need Pul+, Dir+ and Ena (unconnected in my case). What should I do with the rest of the wires (Pul-, Dir- and Ena).

Thank you

It is getting difficult to help because I don't know your background and don't have a clue about your wiring or who did the original work, but I'll make a new effort.

1. If you are sure you NEVER will use the enable signal then you don't have to care about that, so just ignore as it is ignored in your picture.
2. Check PUL - and DIR - with a DMM, I think those are connected to the same source, so basically you could have only the blue wire connected and from that bridge to PUL -.
3. In theory, if both your controlling devices share a common signal ground then you don't need to switch that signal, but it is a good engineering practice to do it, so I would definitely switch that also.
4. This leaves you with three signals to switch and these are the same as PUL + , DIR + and DIR -. Remember that DIR - is bridged to PUL - otherwise it will not work.

In the end, according to the above, you will need a relay which can switch three signals, but you won't find such relay. They are always made as 1, 2 or 4 (or more) pole relays.