I am looking for a way to improve the workflow in a PHP based CMS. There is a lot of switching between the editor mode and the preview mode of the page. The editor mode is h
What about using iframes and JavaScript?
I know you said you want to avoid 'confusion using iframes', but in my opinion if you really need to load different pages at the same time this is the best option.
In theory, you could create your own tab system using javascript or even better, using jQuery, because its UI module offers pretty cool tab control.
For every tab you could load separate "headerless-footerless" version of your specific admin page inside element. If user wanted to modify something different, he will simply click on the tab and bring different iframe.
All this could also be done using AJAX, but iframe solution is quite easy as you just need to load ready page and all postbacks are already handled by original page and separated from master-admin-page.
You might also need to play a little bit to set correct height of your iframe to fit all the content without scrollbars, but this again, is just bit of javascript.