Maya - Workspace.mel - how do you set custom folders?

We are currently trying to manipulate the custom folders available in the Maya File Open dialog (lower left hand corner of the window).

Usually we would do this with a custom workspace.mel file, for example:

workspace -fr "scene" "scenes/3d";

Would set a folder pointing to the scenes/3d folder under whatever we've set the $MAYA_PROJECT env var.

Now in

 

It states

// The following example shows how to set multiple paths into a fileRule value
workspace -fileRule 'newMultiPathFileRuleName' '/h/userName/maya/projects/default;newFileRuleValue';

and 

So ideally, we should be able to set multiple file paths for the "scenes" fileRuleName by using "scenes/3d/anim:scenes/3d/model" or more precisely:

workspace -fr "scene" "scenes/3d/anim:scenes/3d/model"

Using this "should" do something, preferably populate that custom folder bar in the lower left hand corner with two directories.  Alas it does not, in fact it does nothing, throws no errors and is generally useless.

So, the question is how do we add project relative paths to the file open dialog?

Additionally it looks like there are only certain fileRuleNames that will populate this area, those being the default names (scenes, assets, images, sourceimages, renderData, clips, sound, scripts, data, movies, autosave), but it would be great if either the multi file path worked because we actually store maya files in very specific directories and want to make those available.

Is anyone out there populating this window using workspace.mel to populate this in a sensible way or are you doing it some other way (ie. overriding the np_get* files with your custom scripts folder)

Thanks,