Personalizar tamaño texto en títulos y encabezados

You can customize the default header sizes by adding something like the below to the "Custom HTML Head Content" setting:

<style>
.page-content h1 { font-size: 2rem; }
.page-content h2 { font-size: 1.8rem; }
.page-content h3 { font-size: 1.6rem; }
.page-content h4 { font-size: 1.4rem; }
.page-content h5 { font-size: 1.3rem; }
.page-content h6 { font-size: 1.15rem; }
</style>

https://github.com/BookStackApp/BookStack/issues/462#issuecomment-786803638