Hook theme path to template in a folder
Drupal uses filenames only for theme suggestions 'template' =&gt; 'my_wall1'. But you can still place the template in a subfolder below templates and Drupal will still discover it.

Not tried this myself, but according to hook_theme() documentation: You can add a drupal root relative path if you want a very specific directory for the Twig file:

function my_module_theme() {
  return [
    'wall1' =&gt; [
      'template'  =&gt; 'my_wall1',
      'variables' =&gt; [
        'w1' =&gt; NULL
      ],
      'path' =&gt; 'DRUPAL_ROOT_RELATIVE_PATH'
    ],
  ];
}