WordPress visual editor tinymce how to preserve custom attributes
You need to add your custom attributes to valid_elements in the tinymce init
valid_elements: "@[id|class|title|style|data-initial|...]," + //Your attributes HERE!!! "a[name|href|target|title]," + "#p,-ol,-ul,-li,br,img[src],-sub,-sup,-b,-i," + "-span,hr",in order to keep them in the editor - otherwise the tinymce cleanup functionality will remove them (because they are not valid).
use extended_valid_elements to add your custom attribute to existing rule . using valid_elements will break current rule
this is my example
$args = array( 'textarea_rows' = > 15, 'teeny' = > true, 'quicktags' = > true, 'media_buttons' = > false, 'tinymce' = > array('extended_valid_elements' = > "@[data-initial]"));wp_editor(get_post_meta($post_id, 'spintaxed_cnt', 1), 'spinner-editor', $args);