I had the same problem so i decided to help some more people out.
Now to enable it in MODx we have to create the new plugin for it by doing the following:
&customparams=Custom Parameters;textarea; &mce_formats=Block Formats;text;p,h1,h2,h3,h4,h5,h6,div,blockquote,code,pre &entity_encoding=Entity Encoding;list;named,numeric,raw;named &entities=Entities;text; &mce_path_options=Path Options;list;rootrelative,docrelative,fullpathurl;docrelative &mce_resizing=Advanced Resizing;list;true,false;true &disabledButtons=Disabled Buttons;text; &link_list=Link List;list;enabled,disabled;enabled &webtheme=Web Theme;list;simple,editor,creative,custom;simple &webPlugins=Web Plugins;text;style,advimage,advlink,searchreplace,contextmenu,paste,fullscreen,nonbreaking,xhtmlxtras,visualchars,media &webButtons1=Web Buttons 1;text;undo,redo,selectall,|,pastetext,pasteword,|,search,replace,|,nonbreaking,hr,charmap,|,image,link,unlink,anchor,media,|,cleanup,removeformat,|,fullscreen,code,help &webButtons2=Web Buttons 2;text;bold,italic,underline,strikethrough,sub,sup,|,|,blockquote,bullist,numlist,outdent,indent,|,justifyleft,justifycenter,justifyright,justifyfull,|,styleselect,formatselect,|,styleprops &webButtons3=Web Buttons 3;text; &webButtons4=Web Buttons 4;text; &webAlign=Web Toolbar Alignment;list;ltr,rtl;ltr &width=Width;text;100% &height=Height;text;400
Now we have a newly created plugin and we should only disable the old one by going to the old TinyMCE plugin and checking the Disabled box and click save. Make sure you empty your cache and maybe a relog.