A Module Extension defines optional additional components to a Module. Each extension is defined in its own file separate from the main Module file. Extensions are managed from the Module Library window. When the module is loaded to play a game, all its active extensions will be loaded as well.

To install an extension, right-click (Mac users: Command-click) on the module in the Module Library window, choose 'Add Extension' and select the downloaded extension. The extension is automatically activated.

If a module has already been configured with one or more extensions, the Module Library will show a twisty (">") in the left margin next to the module name. The extension may be Deactivated or re-Activated by opening the twisty, right-clicking on the extension file name (.vmdx) and selecting the appropriate option.

When a module is edited, only the module is loaded. To edit an extension, open the twisty and right-click on the extension file name (.vmdx) and select "Edit extension".

In order to create a new extension, right-click on the module and select "New Extension".

Editing a Module Extension is done exactly like editing a Module, by adding and modifying components in the Configuration Window. The only difference is that you cannot delete or modify components of the main Module while editing an extension. Any components in an extension will always be added after those related components in the main Module.