How to create nested paragraphs items programmatically?
After two days, finally, i got it working.
Step 3 is not necessary. My error was in step 2, where I wrote badly the bundle name :-(
so it was

new ParagraphsItemEntity(
    array(
      'field_name' =&gt; 'field_acordeon_hijo',
      'bundle' =&gt; 'acordeon_hijo'))


note the underscore in acordeon_hijo