Hi,
Welcome to post here!
1,If you want to create and manage the Central Store for Group Policy Administrative Templates in Windows, we need to create a folder named PolicyDefinitions under %systemroot%\sysvol\domain\policies as you already.
https://support.microsoft.com/en-us/help/3087759/how-to-create-and-manage-the-central-store-for-group-policy-administra
When you said it was not possible to see all other templates,it is because we need copy all the files to it or down load it .
For example, we copy all the files under from one of your DCs under %systemroot%\PolicyDefinitions . Then the files will all display.
Then you have to copy the msedge.admx file to the PolicyDefinitions folder in systemroot%\sysvol\domain\policies\PolicyDefinitions
Copy the msedge.adml file to the PolicyDefinitions folder in systemroot%\sysvol\domain\policies\PolicyDefinitions
2,If you don't want to use the central store, delete the PolicyDefinitions folder under %systemroot%\sysvol\domain\policies(it is not existed by default)if you have already created it.
Copy the msedge.admx file to PolicyDefinitions under %systemroot%\PolicyDefinitions for all your DCs
Copy the msedge.adml file to PolicyDefinitions under %systemroot%\PolicyDefinitions for all your DCs
Best Regards,