jbmw look at the “tinymce” setting https://codex.www.ads-software.com/Function_Reference/wp_editor
Looks like you can pass setting directly to tinymce.
So it would be something like
<?php
$tinymcesetting = array("theme_advanced_buttons1" => "bold,italic,underline,separator,bullist,numlist,separator,undo,redo");
wp_editor( $content, $editor_id, array("tinymce" => $tinymcesettings));
?>
Actually… scratch all that just do this with the code you already have;
wp_editor( $content, $editor_id, array(“tinymce” => $a));