Without plug
You need to download the "table" folder from the TinyMCE editor package
https://www.tinymce.com/download/
tinymce -> js -> tinymce -> plugins
And copy it to your folder called 'tinymce-plugins'
Then register js by adding a folder to your wp content

Then in your function.php register click
function add_the_table_button( $buttons ) {
array_push( $buttons, 'separator', 'table' );
return $buttons;
}
add_filter( 'mce_buttons', 'add_the_table_button' );
function add_the_table_plugin( $plugins ) {
$plugins['table'] = content_url() . '/tinymce-plugins/table/plugin.min.js';
return $plugins;
}
add_filter( 'mce_external_plugins', 'add_the_table_plugin' );
Then BOOM! table functionality activated

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