Put the pink stick into the blue tube and push the stick to lock it.
Push it again to get the stick out.
The interaction between the blue spring pins (sliding in the radial holes of the yellow hollow cylinder) and the blue outer tube performs the locking function.
The red springs tend to push the blue spring pins outward.
The interaction between the red pins (fixed to the yellow hollow cylinder) and the fixed inner barrel cam maintains the push-push function. Watch an explanatory video:
   • Push-push button 1a  
The blue spring tends to push the yellow hollow cylinder up.
The fixed inner barrel cam is divided into two halves for ease of assembly.
The brown arrow represents the user's push action.
This video is an attempt to decipher the mechanism inside the cane shown at
   • Burger Custom Canes -Titanium Stilett...  

STEP files of this video:
https://www.mediafire.com/file/kxaevw...
Inventor files of this video:
https://www.mediafire.com/file/t2b01z...