JSFiddle - React, Tailwind, and code Playground

HTML

<input id="addForm" type="button" value="mostrar formulario"/>
<form id="form" class="">
    <input id="addBlock" type="button" value="mostrar bloque"/>
    <fieldset id="block">
        <legend>bloque</legend>
        <span>... elementos de formulario ...</span>
    </fieldset>
</form>

CSS

form, input[type="button"]{
padding:1em;
}
form{
background: whitesmoke;
margin:1em 0;
}
fieldset{
    border: 1px dotted gray;
    padding:1em;
    margin: 1em 0 0 0;
}

/********************************/
#form, #block{display:none;}
.activo{display:block !important;}

JavaScript

window.onload = function(){
    var addForm  = document.getElementById("addForm");
    var addBlock = document.getElementById("addBlock");
    var form     = document.getElementById("form");
    var block    = document.getElementById("block");
    
    addForm.onclick = function(){
        form.className = "activo";    
    }
    addBlock.onclick = function(){       
        if(addBlock.value == "mostrar bloque"){                
            block.className = "activo";  
            addBlock.value = "ocultar bloque";    
        }
        else{
            block.className = "";      
            addBlock.value = "mostrar bloque";                
        }       
    }
}