Many thanks for replies. I'm aware of the isofix anchors but that was not what I meant, probably my question was not clear enough. π
So our seat is Besafe Stretch which will be fastened to the car with cars own 3 point seat belt AND 2 pcs of anchor straps for which I needed the anchoring points.
However I happened to find from besafe youtube channel an installation example in which separate anchor lines are routed under the seat and besafe is then connected to these straps, this installation was made for front seat but basically it should be possible for other seat positions as well. Is there any space under the middle row seat. Strap itself needs just ~0,5cm or so.
In case my explanation still is not clear, here's the installation video clarifying above text π
Important part 0:30->1:10
https://youtu.be/KAWYwigleVw?si=XUI1GMbd50-Kv1oy