In Tip 2882, Steps 14 - 22, I created a simple MMC Snap-in for editing GPOs.
Microsoft has written Knowledge Base article Q230263 - How to Create Custom MMC Snap-in Tools Using Microsoft Management Console, which begins:
"Administrators can use Microsoft Management Console (Mmc.exe) to create special tools to delegate specific administrative tasks to users or groups. Saved as MMC console (.msc) files, these custom tools can be sent by e-mail, shared in a network folder, or posted on the Web. They can also be assigned to users, groups, or computers with system policy settings. A tool can be scaled up or down, integrated seamlessly into the operating system, repackaged, and customized. This article describes how to accomplish these tasks."