Timing belt replaced on a 1Z engine, year of manufacture 1996

Hello,
I replaced the timing belt after 100,000 kilometers.

Condition of the timing belt: Very good.
Condition of the tensioner pulley (Ruville): Slight play in the bearing.
Condition of the idler pulley (still original VAG): No play.
Condition of the Conti ribbed belt (with A/C): Severely worn. Broken ribs. Now I finally know where that strange noise was coming from when idling. I had already replaced the tensioner roller, which would have saved me some trouble.

Piston stroke after installing the new belt: 0.48 mm. It had to be readjusted.
I had loosened the camshaft sprocket to allow for the installation of the belt.

I had a huge problem with the right-hand screw (stud bolt/set screw) of the lower timing cover, which had come loose. It took me 2 hours to find a way to get that screw back in without having to completely disassemble the engine.

Question: What are you doing with this screw?