This plugin allows you to enable the mule dupe, also know as IDD on your server. The plugin is based on SweetAnarchy's IDD plugin.
This plugin supports both spigot and paper servers.
There is only one option right now: dupeMultiplier
. This option controls how many items are duped at once. For example, if you wanted to dupe oneulker and this value was set to two, you would end up with 2 shulkers after duping. If the value is 3, then you will have 3 shulkers etc.