Installation of additional insulation for underfloor heating - cables lie on the raw floor slab

I am also definitely in favor. Anything else would be botched work and could become expensive.

Is it the same with the water pipes?
For the pipes coming from the wall, the connection pipes have also already been laid on the floor. The same was true for the drainage system at our new neighbor who is also currently building. The pipes are also nailed to the floor.
But for the drainage, it is correct that the plumber first pulls the pipes, then the wall is plastered, and then the insulation for the underfloor heating is laid, right?
Otherwise, the insulation would be completely ruined by the plasterers.

It's not about the insulation yet, but rather that the complete sealing is missing first... I would then also install the insulation including underfloor heating and screed and then have the plasterer come.

But the process is correct, that first the plumber pulls the pipes, then the wall is plastered, and then the insulation for the underfloor heating is laid, isn't it?

Yes, the process is correct - only the waterproofing has to come beforehand.
You can use the Gefitas 300, but it only sticks if you scrub the wall barrier membranes spotless beforehand.
Laying the membranes under the cables will be fun - no one has thought further than the tip of their own nose.

You can use the Gefitas 300, but it will only stick if you scrub the masonry barrier membranes spotless beforehand.

But then I also need a separate adhesive tape to attach the foil to the masonry barrier membrane? The moisture barrier has adhesive strips only on the edges. So the end side doesn’t stick. I assume there is special adhesive tape for that?

The band is called Siga Sicrall.