Adding style to All H3 inside a container

Design help Custom code
1

Hello, I’d like some help on this:

How can I apply style to all H3s inside a specific container, without having to add a class?

Something like this:

.container h3 {
property: value;
line-height: 30px;
}

2

You can’t do this in the designer but you can with custom code. You can only nest inside rich text elements/fields when it has a class in the designer.