Plugin Default Properties allows you to preselect and set properties for plugins that you intend to use in your application. This is particularly useful when you use plugins that share common setup. An example would be the Email plugin. By setting its default properties, you will not need to enter the mail server details every time you use the plugin.
The functionality of Plugin Default Properties in Joget v3 is at an application-level implementation, instead of the system-wide implementation in Joget v2.