Sorry for the delay. I think there are 2 solutions for this case:

//javascript
$('#example').DataTable({
    ...
    buttons: [
        {
            extend: 'colvis',
            // Exclude any column with the 'noVis' class
            columns: ':not(.noVis)' 
        }
    ],
    columnDefs: [
        {
            targets: [0], // For example, the first column
            className: 'noVis'
        }
    ]
});

or:

// javascript
buttons: [
    {
        extend: 'colvis',
        // Only show columns 1, 2, 3, 4, and 5 in the menu
        columns: [1, 2, 3, 4, 5] 
    }
]

Pls convert this javascript to PHP array in your DataTables widget. Let us know how they work for you.