How to use custom tokens in view header Drupal 8
One possible soliton is to simply when declaring your custom tokens in hook_token_info()

use $info['tokens']['view']

Ex: 

$info['tokens'] = [
    'view' =&gt; [
       'my-custom-token' =&gt; [
          'name' =&gt; t('Custom Token'),
          'description' =&gt; t('A custom token I created.'),
       ],
       // 'my-second-custom-token' =&gt; [...
    ],
];