Cannot adjust dropbolt on bifold doors which is catching
That is called a manual flush bolt. The piece that protrudes through the top and bottom of the door is called the bolt head.

Both the bolt head (which is threaded to an actuating rod), and the actuating rod (which is threaded to the lever actuator) are designed to be adjusted by threading them in or out. The bolt head is commonly keyed, i.e. it is not round but designed with a flat spot (like a "D" shape) and protrudes through a guide plate (attached to the top and bottom of the door) which is also keyed, to prevent the bolt head from turning, which would change the length/adjustment.

You need to thread the bolt head and/or rod in to shorten the flush bolt throw length. The proper way would be to remove the door and lay it flat, then remove the guide. You could try turning it while the door is still hung, using long nose pliers or similar tool; but if the bolt head is keyed and a guide is installed it wont turn, by design.