Hidden Staircase Room is used to hide yourself in between the stairs. Enter the room and pull the lever to cover it up with stairs. Go through the guide and follow step-by-step instructions to make a Hidden Staircase Room.
First, you have to place 4 smooth quartz blocks on the ground and two pistons at the top and four at the back of these blocks as shown in the image below.
Add redstone dust at the top of quartz blocks and redstone repeaters at the back of these two blocks. Place two observers at the back side in the same way as shown in the image below.
Add redstone repeaters next to the observers and set them to maximum delay. And then add some redstone dust around the observers in order to connect the repeaters.
The next thing you need to do is to add two more observers at the top of repeaters. And then place two quartz blocks at the top of these observers.
Place 4 quartz stairs on the pistons.
Add a lever on the ground and connect it with repeaters using redstone dust. Pull the lever and pistons will take the stairs up, pull the lever back in order to drop them back.
Add a layer of stairs on the left and right side of these stairs.
Pull the lever back to bring down the middle of these stairs. And then use smooth quartz blocks to build a secret room under the stairs.
Now you can hide this secret room by pulling the lever.