Save time by associating a keyboard shortcut with the extension command in Xcode > Preferences... > Key Bindings menu.

In my example, I defined short ⌃⇧D for the primary command of extension SwiftPlantUML.

Note: You should choose a shortcut that does not conflict with the default binding.

My shortcut allows me to quickly generate a class diagram for the currently selected source code.

Source editor extensions can read and modify the contents of a source file and read and modify the current text selection within the editor. More cool extensions are listed in the GitHub repository awesome-xcode-extensions.