If you're willing to do a minor edit to the DEA:
- Tools > Plugins (on the main menu) to open the Plugins dialog.
- More>> to reveal an additonal set of actions.
- Single click on the DEA in the list on the left, and then click the Edit... button on the right
- The 4th line down will say @Subtype: followed by one or two template names e.g. @Subtype: "Civil Registration Certificate", "Church Register"
- Add your custom template name to the end of this list, separated by a comma from the previous one and enclosed in double quotes
- At the top of the editor window, choose File > Save As and give your modified DEA a new name (this will prevent it from being overwritten by a new version of the original DEA if you forget and upgrade it.
- Close the editor window.