Marketing Cloud : Data Extension Manager || Explanation here: https://vijayasankarn.wordpress.com/2021/01/18/marketing-cloud-programmatically-export-data-extension/

Data Extension Export CSV.block

<script runat="server" language="JavaScript">
    Platform.Load("core","1.1.2");
    try {
        var DE_CustomerKey = Request.GetQueryStringParameter("de_key");
        var DE = DataExtension.Init(DE_CustomerKey);
        var DEName = DataExtension.Retrieve({Property:"CustomerKey",SimpleOperator:"equals",Value:DE_CustomerKey})[0].Name;
        var DEFields = DE.Fields.Retrieve();

        var DEFieldsList = [];
        for (var i = 0; i < DEFields.length; i++) {
            DEFieldsList.push(DEFields[i].Name);
        }
        Write(DEFieldsList.join());
        Write("\r\n");

        var DERows = DE.Rows.Retrieve();
        for (var i = 0; i < DERows.length; i++) {
            var DERowsList = [];
            var record = DERows[i];
            for(var j = 0; j < DEFieldsList.length; j++) {
                DERowsList.push(record[DEFieldsList[j]]);
            }
            Write(DERowsList.join());
            Write("\r\n");
        }
        HTTPHeader.SetValue("content-disposition","attachment; filename=" + DEName + ".csv");
    } catch(e) {
        Write(Stringify(e));
    }
</script>

Data Extension Manager.block

<script runat="server" language="JavaScript">
    Platform.Load("core","1.1.2");
    try {
        var DESearchOperand = Request.GetQueryStringParameter("DESearchOperand") || "CustomerKey";
        var DENameOperator = Request.GetQueryStringParameter("DENameOperator") || "equals";
        var DENameOperand = Request.GetQueryStringParameter("DENameOperand") || null;
        
        Variable.SetValue("DESearchOperand", DESearchOperand);
        Variable.SetValue("DENameOperator", DENameOperator);
        Variable.SetValue("DENameOperand", DENameOperand);

        if(DENameOperand != null) {
            var DEList = DataExtension.Retrieve({
                Property: DESearchOperand,
                SimpleOperator: DENameOperator,
                Value: (DENameOperator == "in" ? DENameOperand.split(",") : DENameOperand)
            });

            var DETableRows = [];
            for (var i = 0; i < DEList.length; i++) {
                // Name
                var tempVar = "<td>" + DEList[i].Name + "</td>";
                tempVar += "<td>" + DEList[i].CustomerKey + "</td>";

                // Folder Path
                var folderPath = [];
                var path = function(id) {
                    if (id> 0) {
                        var results = Folder.Retrieve({Property:"ID",SimpleOperator:"equals",Value:id});
                        folderPath.unshift(results [0].Name);
                        return path(results[0].ParentFolder.ID);
                    } else {
                        return id;
                    }
                };
                path(DEList[i].CategoryID);
                tempVar += "<td>" + folderPath.join(" ⇒ ") + "</td>";

                // Operation
                var operationString = '<a href="https://abc.xyz/downloadCSV?de_key=' +  DEList[i].CustomerKey + '" title="Export CSV">⇩</a>';
                operationString += '<a href="https://abc.xyz/viewInTable?de_key=' +  DEList[i].CustomerKey + '" title="View in Table">👁</a>';
                tempVar += "<td>" + operationString + "</td>";

                DETableRows.push(tempVar);
            }
            Variable.SetValue("DETableRows", DETableRows);
        }
    } catch(e) {
        Write(Stringify(e));
    }
</script>

<style>
    a {
        text-decoration: none;
        padding-right: 0.5rem;
    }
</style>
<h1 style="text-align: center">DATA EXTENSION MANAGER</h1>

<form method="post">
    Get Data Extension(s) whose 
    <select name="DESearchOperand">
        <option %%=IIF(@DESearchOperand=="CustomerKey", "Selected", "")=%% value="CustomerKey" %%=IIF(@DESearchOperand=="CustomerKey", "Selected", "")=%%>External Key</option>
        <option value="Name" %%=IIF(@DESearchOperand=="Name", "Selected", "")=%%>Data Extension Name</option>
    </select>
    <select name="DENameOperator">
        <option %%=IIF(@DENameOperator=="equals", "Selected", "")=%%>equals</option>
        <option %%=IIF(@DENameOperator=="notEquals", "Selected", "")=%%>notEquals</option>
        <option %%=IIF(@DENameOperator=="in", "Selected", "")=%%>in</option>
        <option %%=IIF(@DENameOperator=="like", "Selected", "")=%%>like</option>
    </select>
    <input type="text" name="DENameOperand" value="%%=v(@DENameOperand)=%%">
    <input type="submit">
</form>

%%[ IF ROWCOUNT(@DETableRows) > 0 THEN ]%%
<table border="1" cellpadding="7">
    <thead>
        <th>Data Extension Name</th>
        <th>Data Extension External Key</th>
        <th>Path</th>
        <th>Operation</th>
    </thead>
    <tbody>
        %%[ 
            FOR @I = 1 TO ROWCOUNT(@DETableRows) DO             
        ]%%
        <tr>
            %%=v(Row(@DETableRows, @I))=%%
        </tr>
		%%[ NEXT @I ]%%
    </tbody>
</table>
%%[ ENDIF ]%%

Data Extension Viewer.block

<script runat="server" language="JavaScript">
    Platform.Load("core","1.1.2");
    try {
        var DE_CustomerKey = Request.GetQueryStringParameter("de_key");
        var DE = DataExtension.Init(DE_CustomerKey);
        var DEName = DataExtension.Retrieve({Property:"CustomerKey",SimpleOperator:"equals",Value:DE_CustomerKey})[0].Name;
        var DEFields = DE.Fields.Retrieve();

        var DEFieldsList = [];
        Write("<table border='1' cellpadding='7'>");
        Write("<th>");
        for (var i = 0; i < DEFields.length; i++) {
            DEFieldsList.push(DEFields[i].Name);
        }
        Write(DEFieldsList.join("</th><th>"));
        Write("</th>");

        var DERows = DE.Rows.Retrieve();
        for (var i = 0; i < DERows.length; i++) {
            var DERowsList = [];
            var record = DERows[i];
          
            Write("<tr><td>");
            for(var j = 0; j < DEFieldsList.length; j++) {
                DERowsList.push(record[DEFieldsList[j]]);
            }
            Write(DERowsList.join("</td><td>"));
            Write("</td></tr><br/>");
        }
       Write("</table>");
    } catch(e) {
        Write(Stringify(e));
    }
</script>

Thanks for sharing such a wonderful and helpful article :)

Can you also add the code for "viewCSV" code block, which would help the community.

@cvvishalkumar, those are the cloud pages that we need to create and embed these blocks into it. Here's the explanation on making these to work: https://vijayasankarn.wordpress.com/2021/01/18/marketing-cloud-programmatically-export-data-extension/

Thanks for sharing such a wonderful and helpful article :)

Can you also add the code for "viewCSV" code block, which would help the community.

It has been added now!