How to close cracks in rough plaster?

We have a timber frame house with thermal insulation. Currently, only the rough plaster is applied or the preparatory work for the fine plaster is completed. Unfortunately, I did not lay any cables for the motion detectors. The motion detectors are to be connected to 230V and their outputs will then be processed via the KNX binary input. So, there is no high load through the cable.

Now my exciting question: Can I simply open the rough plaster with a wall chaser and lay the cables there? The construction company will still apply the fine plaster. However, I want to close the slots myself beforehand. What is the best way to do this? Is there normal gypsum/plaster and mesh for this?

Now the question is what kind of rough plaster is on it. There is simple plaster and masonry mortar, or gypsum plaster. It should be easy to apply again.

Now the question is what kind of coarse plaster is on there. There is simple plaster and masonry mortar, or gypsum plaster. You should be able to just smear it on again.

There is not only "simple plaster."
Masonry mortar is not used for plastering.
Gypsum plaster only belongs in dry interior areas.
It is not (anymore) easy to just smear on.

With the so-called "coarse plaster," reinforcing mesh should have been embedded. If a long slit is now made, the painting company will, with a probability bordering on certainty, not guarantee against cracking.