Listing/Itemizing Installed Extensions

I did a quick scan, and I couldn’t find the answer to this question, but my apologies if this is obvious.

I want to itemize the installed extensions, and just the extensions, that I have installed. How can I go about doing that? I can see the list of everything that is installed, but it’s not jumping out to me which extensions/plugins are those that do not come with the base install. Obviously I don’t want to uninstall anything that is part of the required set.

My reference set is Orange and RapidMiner, where the delineation between “base” and extensions is pretty straight forward.