If nothing is currently recorded in the land register, then no right of way exists and you can close off the access! Here you would have an approach to impose the paving costs on the neighbors in exchange for a right of way. Of course, this only works if the properties can also be accessed otherwise and you have a thick skin for neighborhood disputes
Addendum: There is a current BGH ruling on this. Google "BGH decides: No right of way by habit".
Hello, although there is no right of way by habit, there is a necessity right of way if the property cannot otherwise be reached from a public area. That means the neighbor of the rear property has the right to have a right of way registered in the land register. But—with the registration of the necessity right of way, the conditions can be included. This is on the one hand a necessity right of way rent (a kind of lease, calculated from the interest on the value of the way) and on the other hand also the maintenance obligations (cleaning, repair costs, ...).
I have all this on a property that belongs to me. Unfortunately, my ancestors forgot about the necessity right of way rent back then, or exchanged it for a personal right of way across the neighbor’s property to their utility garden. The garden can be reached, albeit by a considerable detour, via a public road and thus this right of way no longer exists today.