If that black plastic preload bolt is the last boring piece of hardware on your bike, the Kogel Shimano Crank Arm Fixing Bolt is the answer. Available in black, blue, silver, red, and gold, it replaces the stock part with an anodized 6061-T6 alloy part.
They come in two lengths, Short (7mm) and Long (13mm) to match which ever length came with your crankset. You’ll need a Shimano II Crank Arm Bolt Tool (TL-FC16 or Park Tool BBT-10.2). Just snug them down until there’s no play in your cranks, back it off a hair, then torque the crank arm’s pinch bolts to spec.
Just remove your stock plastic bolt first and measure so you get the correct length, but basically the short one goes with GRX, XT and SLX (mountain and gravel stuff), and the long one goes with the road cranks, but if you have an older road setup, it’s best to measure. They’re available direct at Kogel.cc for $24.99 each.