Here is my attempt at making hidden stairs for a building.

Included is my world save with a very simple building design to show off my idea.

However the design included in the building the redstone wiring is very spread out and i redesigned it to not take up any more than 3 tiles from the stairs making it more compact.

This is also in the world save.

Might be of no use to anyone, but it was my learning curve for redstone wiring.

There is 3 wiring colours they are:

PURPLE - wiring for the stairs
ORANGE - Turns the stairs off
GREEN - Turns the stairs on

This uses a NOR switch for making buttons act like levers so the stairs stay active.
Could probably be simplified but im not that good at redstone yet.

Enjoy