How to do a nested if else statement in ReactJS JSX?

You can nest as many statements as possible. please follow this code assuming that this.state.firstTestValue, this.state.someTestValue and this.state.thirdValueTest are your test values from the state.

{this.state.firstTestValue
    ? <div >First Title</div>
    : [
        this.state.someTestValue
            ? <div>Second Title</div>
            : [
                this.state.thirdValueTest 
                ? <div>Some Third Title</div> 
                : <div>Last Title</div>
            ]
    ]
}

You need to wrap your title and body in a container. That could be a div. If you use a fragment instead, you'll have one less element in the dom.

{ this.state.loadingPage
  ? <span className="sr-only">Loading... Registered Devices</span>
  : <>
      {this.state.someBoolean
        ? <div>some title</div>
        : null
      }
      <div>body</div>
    </>
}

I would advise against nesting ternary statements because it's hard to read. Sometimes it's more elegant to "return early" than to use a ternary. Also, you can use isBool && component if you only want the true part of the ternary.

renderContent() {
  if (this.state.loadingPage) {
    return <span className="sr-only">Loading... Registered Devices</span>;
  }

  return (
    <>
      {this.state.someBoolean && <div>some title</div>}
      <div>body</div>
    </>
  );
}

render() {
  return <div className="outer-wrapper">{ this.renderContent() }</div>;
}

Caveat to the syntax someBoolean && "stuff": if by mistake, someBoolean is set to 0 or NaN, that Number will be rendered to the DOM. So if the "boolean" might be a falsy Number, it's safer to use (someBoolean ? "stuff" : null).

Instead of nesting ternary operators as it is often suggested or creating a separate function that will not be reused anywhere else, you can simply call an inline expression:

<div className="some-container">
{
   (() => {
       if (conditionOne)
          return <span>One</span>
       if (conditionTwo)
          return <span>Two</span>
       else (conditionOne)
          return <span>Three</span>
   })()
}
</div>

You can check multiple conditions to render components accordingly like below:

  this.state.route === 'projects'
  ? 
  <div> <Navigation onRouteChange={this.onRouteChange}/> Projects</div>
  :
  this.state.route === 'about'
  ?
  <div> <Navigation onRouteChange={this.onRouteChange}/> About</div>
  :
  this.state.route === 'contact'
  ?
  <div> <Navigation onRouteChange={this.onRouteChange}/> Contact</div>
  :
  <p> default </p>