ᐅ The connection for the washing machine was omitted in the new build.

Hope2020 schrieb:

That is definitely the best idea for now. However, it is quite surprising that all the other trades stayed silent about it and we had to notice it ourselves.

Well, the trades involved afterwards have no interest in what kind of connections you ordered. The plumber handles that during the rough-in phase. After that, the plasterer covers what’s there, and the tiler tiles over it.

That is true, but even the plumber was constantly on site. Well, that’s how it is now. We will make the best of it.

Hope2020 schrieb:

That’s true, but even the plumber was constantly on site. Well, it is what it is now. We’ll make the best of it.

Feel free to let us know how it turned out.

A washing machine has three connections: fresh water, waste water, and electricity. I assume this concerns the fresh water or waste water, or both?
Would the machine need to be located somewhere other than originally planned?

Hope2020 schrieb:

Presumably, the general contractor will want to connect at the sink. Do we have to accept this, or can we request the plumbing to be routed inside the wall?

Most likely, the water supply and drain from the sink will be used, yes.
I believe the effort involved in relocating the pipes inside the wall is no longer reasonable. Besides, the washing machine and sink will cover most (if not all) of the installation, so there's no need to be overly particular at this point.
However, I would try to negotiate something in return, such as a dedicated electrical circuit for the washing machine or a built-in pedestal. Something like that would provide clearer added value.

Hope2020 schrieb:

That is probably the best idea to start with. However, it is quite surprising that all the other craftsmen remained silent about it and we only noticed it ourselves.

A naive assumption. The other trades just do their own work. None of them knows whether you ordered it that way to save costs.
As an electrical engineer, I don't care what the other trades are doing next to me. Why should I? The client pays me for my part, not for freely uncovering the mistakes of others...
I actually benefit when I can say later, in case of problems, "Well, company XYZ prepared/performed this poorly; we couldn’t do better. The preparatory work was their responsibility. We can fix it, but that would require a change order."
My experience from 15 years in plant engineering:
Clients do not appreciate being informed about such issues beforehand; in the end, you get stupid comments and the extra effort to adjust on my side is brushed off because "It could still be corrected on the system side in time."

Even the installer only knows what his supervisor tells him, because the supervisor is on site during the walkthrough, not the journeyman who actually carries out the work.
If the supervisor says, "Just install the rough-in, no washing machine was requested," the installer doesn’t ask further. That’s just how it is—no washing machine, all good.

That’s why you should speak directly to the installers if you notice mistakes, and not assume:
"Alright, they didn’t do it; the supervisor will probably review and fix it."

No. Usually, if a task is not carried out at all (which is different from poor execution), the supervisor simply didn't tell his installers to do it. Then you need to address someone immediately. This usually helps to fix the problem cheaply.
Demanding after the final inspection that something should have been installed concealed in the wall is unrealistic. Completely unrealistic.