I want to know because it sounds like I might use it but the wiki doesn't have a documentation of it.
Edit: I've been guessing what I should do and here is the code:
plugin:CreateDockWidgetPluginGui("Idkwhatthisisfor", DockWidgetPluginGuiInfo.new(Enum.InitialDockState.Right, true, true, 100, 100, true))
But it is just giving me this error: Plugin:CreateDockWidgetPluginGui is not enabled yet
I'm pretty sure that that is for the new PluginGui system coming out soon. There's a little more information about it here, under all of the API changes.