are you talking about a skeleton element that you're using as a placeholder while you wait for data to load?

not exactly
i wan't a div with some id and i want to append a component to it in my client component

You can render components conditionally based on some context state. From your client component you can update the context state and then use it in the navbar to render another component inside it if this is what you're looking for

It's hard to say given the somewhat generic request. It would help if you shard a screenshot of the app or it's folder structure with annotations

in that case i have to make my navbar a client component and i don't want to convert it
i'm looking for something like render(document.getElementById("id") , <Component />)

You don't have to make it a client component. Just add a client component inside it that doesn't render anything until the context state changes to whatever value you set

yea but it's in my layout and where i need to use it is in my page.js and inside <Main /> component
so in order to make it work i have to make layout client component so i can use context

No, you're misunderstanding how client and server components work...
You can have a server component nested inside a client context and still keep it as an rsc. Read this section from the documentation: https://nextjs.org/docs/app/building-your-application/rendering/composition-patterns#supported-pattern-passing-server-components-to-client-components-as-props

is there any aproach like this in nextjs ? :

"use client";

<>
  <SSR>these are converted to ssr</SSR>
  <NoSSR>these are client side renderer</NoSSR>
</>

No, if you place the 'use client' directive in a file you can't import server components in it anymore. You can only pass server components to client components as props.

This is allowed tho:

import { ServerComponentA, ServerComponentB } from './components/server'
import { ClientComponent } from './components/client'

export default async function Page() {
  return (
    <ServerComponentA>
      <ClientComponent>
        <ServerComponentB />
      </ClientComponent>
    </ServerComponentA>
  )
}

thanks alot