This is infuriating when working from a source build. To get the plugins we need, we have to install a binary version of the engine, download the plugin, grab it from the engine plugin folder then immediatelly uninstall the engine again.
This also makes updating plugins in your source builds a nightmare. Downloading the engine is not a short-time job. I understand why this is done for the average user, but for those of us working with source builds this becomes a real pain. We need to be able to download marketplace content, for any engine version, to any arbitrary folder on our machines.