You need to create a template variable that allows you to associate content. It will be a multi-select listbox that has input option values similar to this:
@EVAL return substr($modx->runSnippet('Ditto', array("parents"=>"723","depth"=>"1","display"=>"all","showInMenuOnly"=>"0","sortBy"=>"pagetitle","sortDir"=>"ASC", "tpl"=>"@CODE ||[+pagetitle+]==[+id+]")), 2);
Also, set the widget to delimited list.
Then call this new template variable where it’s needed in the template.