I might be wrong but I think GP is talking about shadow parts[1] my-element::part(custom-selector) { /* ... */ } 1: https://developer.mozilla.or

I might be wrong but I think GP is talking about shadow parts[1] my-element::part(custom-selector) { /* ... */ } 1: https://developer.mozilla.org/en-US/docs/Web/CSS/::part https://developer.mozilla.org/en-US/docs/Web/CSS/::part