ᐅ Windowpane never replaceable again

A question for any legal experts or people who have had similar experiences.
We have a U-shaped reinforced concrete staircase (double turn without an intermediate landing) from the basement (at street level on the street side) up to the ground floor.
“Behind” the staircase is a window to let in more light in the stairwell, so the lights don’t have to be on during the day.
The window is fixed, meaning it is not designed to open (no handle or anything).
So far, so good. We recently considered installing a partially frosted glass pane to reduce visibility of the staircase from outside. At that point, we realized the glass would likely never be removable because the staircase extends all the way to the wall.

The question now is, is it considered a (hidden) defect if a windowpane cannot be replaced without either seriously damaging the staircase or chipping away part of the interior plaster and masonry?
This is not about the other glass for now, since you could use a film in the basement window. But I wonder who would cover the additional costs if the pane, for example, breaks at some point. As mentioned, the wall above the window would have to be partially opened up to pull the pane out upward.

Thank you very much for any answers, opinions, or possibly similar rulings or legal references...