Add a new class using @apply

.fi-header #grid div:last-child {
    @apply grid flex-1 auto-cols-fr p-6 gap-y-8 fi-ta-ctn divide-y divide-gray-200 overflow-hidden rounded-xl bg-white shadow-sm ring-1 ring-gray-950/5 dark:divide-white/10 dark:bg-gray-900 dark:ring-white/10;
}

.fi-header #grid div:last-child {
    @apply grid flex-1 auto-cols-fr p-6 gap-y-8 fi-ta-ctn divide-y divide-gray-200 overflow-hidden rounded-xl bg-white shadow-sm ring-1 ring-gray-950/5 dark:divide-white/10 dark:bg-gray-900 dark:ring-white/10;
}

grid flex-1 auto-cols-fr gap-y-8

grid flex-1 auto-cols-fr gap-y-8