It is not possible in PSE11 MacOSX (latest version) to choose an additional plugins-folder for third-party plugins.
This was posisble in PSE9 by the [Choose]-button.
This is clearly an omission in the GUI for PSE11. Please, Adobe correct the bug, or is there another solution ?
in PSE 11, the situation is as follows:
in PSE9, it works by the [Choose]-button:
My old plugin-folder is important to me as I cannot port the old plugins to the default
folder where PSE11 searches for plugins.
Can you try this solution and check if it works for you - http://blogs.adobe.com/pselements/load-plug-ins-at-launch-of-photoshop -elements/. It is for Windows but you can press the corresponding keys on Mac.