"David WE Roberts" wrote

I want to be able to completely unhook the window and swing it right
back against the outside wall like a shutter.

So does anyone know of a window stay which will meet both requirements?

Perfect time for the favorite answer in ukDIY.... ANGLE GRINDER.....

....applied to the end stop, sorted.

As long as there is also an angle un-grinder to refit the end stop.

I need a stay with an easily removable/refittable stop.

'kinell, do you want the moon on a stick too?

Mount the inner end of the slider stay jobby via an easily removable
method... pin that can be pulled out, quarter turn screw or something?