Set the focus of the specified div to 0, tabindex="0" when the mouse clicks on the div, the focus becomes - 1, and execute the function called by onfocus="show1()", show1(). When power transmission and other places, that is, the mouse loses focus, the onblur="unshow1()" operation is performed, that is, the unshowfunction is called.

<div style="margin-top:7px;margin-left:35px" tabindex="0" onfocus="show1()" onblur="unshow1()">
			<a id="new-file" class="button"><font size="2"color="white ">Newly build</font ></a>
					
			<div id="set1" style="border:1px black solid;display:none;position:absolute;margin-left:30px;background-color:white;margin-top:5px;width:142px;height:272px;">
					
			<div class="div_little"style="margin-top:0px;">
				<div style="float:left;margin-left:16px;margin-top:8px"><img src="9.png"/></div>
				<div style="float:left;margin-left:10px;margin-top:8px"><font size=1>New folder</font></div>
				</div>
						
				<div class="div_little">
					<div style="float:left;margin-left:16px;margin-top:8px"><img src="9.png"/></div>
					<div style="float:left;margin-left:10px;margin-top:8px"><font size=1>Import</font></div>
					</div>
						
						<div class="div_little">
								<div style="float:left;margin-left:16px;margin-top:8px"><img src="9.png"/></div>
								<div style="float:left;margin-left:10px;margin-top:8px"><font size=1>Flow chart</font></div>
						</div>
						<div class="div_little">
								<div style="float:left;margin-left:16px;margin-top:8px"><img src="9.png"/></div>
								<div style="float:left;margin-left:10px;margin-top:8px"><font size=1>Mind mapping</font></div>
						</div>
						<div class="div_little">
								<div style="float:left;margin-left:16px;margin-top:8px"><img src="9.png"/></div>
								<div style="float:left;margin-left:10px;margin-top:8px"><font size=1>Prototype map</font></div>
						</div>
						<div class="div_little">
								<div style="float:left;margin-left:16px;margin-top:8px"><img src="9.png"/></div>
								<div style="float:left;margin-left:10px;margin-top:8px"><font size=1>UML</font></div>
						</div>
						<div class="div_little">
								<div style="float:left;margin-left:16px;margin-top:8px"><img src="9.png"/></div>
								<div style="float:left;margin-left:10px;margin-top:8px"><font size=1>Network Topology</font></div>
						</div>
</div>

Here are two functions:

function show(){
		document.getElementById("set").style.display="";
	}
	function unshow(){
		document.getElementById("set").style.display="none";
	}
	function show1(){
		document.getElementById("set1").style.display="";
	}
	function unshow1(){
		document.getElementById("set1").style.display="none";
	}

Click on the avatar and it appears:

Click elsewhere: The drop-down box disappears: