Every Iris Code finding could be rendered as a squiggle, but that would make the Problems panel less useful rather than more.
The Problems panel is where you look for what is broken right now: compiler errors and type failures. Filling it with forty TODOs and a magic number means it stops being read, which costs more than the TODOs do.
Inline diagnostics are therefore off by default, and when enabled, only the categories most likely to need immediate attention are on.
What is enabled by default
Secrets, security smells, @ts-ignore, unused functions and any usage: findings that usually warrant fixing at the moment you see them.
Structural warnings such as file length stay off. A long file is a property of your project rather than an error, and it should not appear beside a type failure with the same urgency.
Turning it on
Enable it globally, then pick what you want:
"enableInlineDiagnostics": false removes every squiggle and Problems panel entry while leaving all findings visible in the Iris Code sidebar. Nothing stops being detected; it stops being surfaced in the editor.