I typically use one or two of my own customized Eclipse Perspectives when using Domino Designer.
It is easy enough to modify the current perspective and then use the Window - Save Perspective As... menu to save a personalized perspective.
What is a little irritating though is having to go through the "Open Perspective - Other" menu to locate the custom perspective I want to use. I prefer to have my perspective right in the menu.
The choices on the "Open Perspective" menu are controlled by the perspectives themselves and can be customized. By customizing each of the default Designer perspectives, you can choose what choices appear in the menu.
Bam! Once you do that for each of the perspectives (Domino Designer, Forms/Views, Java, Plug-in Development and XPages), your custom perspective will always show up as a quick choice!