Well, depending on what exactly you want to do with Mambo, you can use Maguma to make changes to the php. the benefits are that
Maguma is designed for creating and edity PHP, so the concepts are clearer and the tootip library is geared specifically to php development. So, specifically speaking, if you wanted to modify a php file in Mambo, you could open it in Maguma and see clearly marked the parts of the code.
I use Topstyle Pro for most of the CSS work. I'm assuming that because this question was posted in the template section that you want to modify or create a Mambo template.
Topstyle lite (free version of pro) would help with the css as it has the same benefits as Maguma, only for css rather than php.
A mambo template has 4 main parts:
index.php (The php and html)
template_css.css (the styles and rules for presentation of your content)
templateDetail.xml (an index of your template files and other info)
images (any images that you want in your template)
If you already have a registered copy of DW or have oodles of cash, there is a plugin that has Mambo specific menu items that allow one click population of your index.php file of Mambo hooks and code.
Another free application that has a similar plugin is
html-kit. I'm not a fan of this software, but others swear by it.
I hope this is what you are looking for.
Cheers,
David