If you want to add custom menuitems, modify navbars, add funtionality to toolbars etc. you need to modify so called ISV.config. In CRM 4.0 it can be done pretty easily with these simple steps:
- Export current ISV config: Settings -> Customization -> Export Customizations and then select ISV Config and press Export Selected Customizations.
- Save .zip file and edit .xml file inside it
- Import modified file from Settings -> Customization -> Import Customizations
- Enjoy your modifications!
Actually that same has been presented in really cool Silverlight ScreenCast in here (it's really worth checking out!).
BUT... what if your UI customizations aren't showing up in the UI?! Well the reason is actually pretty obvious (when you found out it first :-)... because you need to first enable the customizations from system settings:
So navigate to Settings -> Administration -> System Settings and you'll get this dialog:
There you can find Custom menus and toolbars which is by default empty. So in order to support your stuff you need to press the ellipse next to the empty textbox and select the UIs you want to modify:
Now I have selected all the three UIs and I'll just press OK for the two dialogs. And now you should really see your own modifications.
Anyways... Happy hacking!